Enigma

1

LATER, IT WOULD transpire that Bletchley Park knew almost everything there was to know about U-653.

They knew she was a Type VIIc – 220 feet long, 20 feet wide, with a submerged displacement of 871 tons and a surface range of 6,500 miles – and that she had been manufactured by the Howaldts Werke of Hamburg, with engines by Blohm und Voss. They knew she was eighteen months old, because they had broken the signals describing her sea-trials in the autumn of 1941. They knew she was under the command of Kapitanleutnant Gerhard Feiler. And they knew that on the night of 28 January 1943 – the final night, as it happened, that Tom Jericho had spent with Claire Romilly – U-653 had slipped her moorings at the French naval port of Saint-Nazaire and had moved out under a dark and moonless sky into the Bay of Biscay to begin her sixth operational tour.

After she had been at sea for a week, the cryptanalysts in Hut 8 broke a signal from U-boat headquarters – then still in their grand apartment building off the Bois de Boulogne in Paris – ordering U-653 to proceed on the surface to naval grid square KD 63 'AT MAXIMUM MAINTAINABLE SPEED WITHOUT REGARD TO THE THREAT FROM THE AIR'.

On 11 February she joined ten other U-boats in a new mid-Atlantic patrol line code-named Ritter.

Weather conditions in the North Atlantic were particularly foul in the winter of 1942-3. There were a hundred days when the U-boats reported winds topping force 7 on the Beaufort scale. Sometimes the gales reached over 100 miles per hour, whipping up waves more than 50 feet high. Snow, sleet, hail and frozen spray lashed submarines and convoys alike. One Allied ship rolled over and sank in minutes simply from the weight of ice on her superstructure.

On 13th February, Feiler broke radio silence to report that his watch officer, one Leutnant Laudon, had been washed overboard – a blatant disregard of operational procedure on Feiler's part which brought no condolences but a terse rebuke from his controllers, broadcast to the entire submarine fleet:

FEILER'S MESSAGE ABOUT LOSS OP WATCH OFFICER SHOULD NOT HAVE BEEN SENT UNTIL W/T SILENCE WAS BROKEN BY GENERAL CONTACT WITH ENEMY.

It was only on the 23rd, after nearly four weeks at sea, that Feiler redeemed himself by at last making contact with a convoy. At 6 p.m. he dived to avoid an escorting destroyer, and then, when night came, rose to attack. He had at his disposal twelve torpedoes, each 23 feet long with its own electric motor, capable of running through a convoy, turning in a half circle and running back, turning again and so on, and on, until either its power ran out or a ship was sunk. The sensing mechanism was crude; it was not unknown for a U-boat to find itself being pursued by its own armaments. They were called FATs: Flachenabsuchendertorpedos, or 'shallow searching torpedoes'. Feiler fired four of them.

FROM: FEILER

IN NAVAL GRID SQUARE BC 6956 AT 0116. FOUR-FAN AT A CONVOY PROCEEDING ON A SOUTHERLY COURSE AT 7 KNOTS. ONE STEAMSHIP OF 6,000 GROSS REGISTERED TONS: LARGE EXPLOSION AND A CLOUD OF SMOKE, THEN NOTHING MORE SEEN. ONE STEAMSHIP OF 5,500 GRT LEFT BURNING. 2 FURTHER HITS HEARD, NO OBSERVATIONS.

On the 25th, Feiler radioed his position. On the 26th, his luck turned bad again.

FROM: U-653

AM IN NAVAL GRID SQUARE BC 8747. HIGH PRESSURE GROUP 2 AND STARBOARD NEGATIVE BUOYANCY TANK UNSERVICEABLE. BALLAST TANK 5 NOT TIGHT. IS MAKING ODD NOISES. DIESEL PRODUCING DENSE WHITE SMOKE.

Headquarters took all night to consult its engineers and replied at ten the following morning.

TO: FEILER

THE CONDITION OF BALLAST TANK NO 5 IS THE ONLY THING WHICH MAY ENFORCE RETURN PASSAGE. DECIDE FOR YOURSELF AND REPORT.

By midnight, Feiler had made his decision.

FROM: U-653 AM NOT RETURNING,

On 3 March, in mountainous seas, U-653 came alongside a U-boat tanker and took on board 65 cubic metres of fuel and provisions sufficient for another fourteen days at sea.

On the 6th, Feiler was ordered into station in a new patrol line, code-named Kaubgraf (Robber Baron).

And that was all.

On 9 March the U-boats abruptly changed their Weather Code Book, Shark was blacked out, and U-653, along with one hundred and thirteen other German submarines then known to be operating in the Atlantic, vanished from Bletchley's view.

At 5 a.m. GMT on Tuesday 16 March, some nine hours after Jericho had parked the Austin and walked into Hut 8, U-653 was heading due east on the surface, returning to France. In the North Atlantic it was 3 a.m. After ten days on station in the Raubgraflme, with no sign of any convoy, Feiler had finally decided to head for home. He had lost, along with Leutnant Laudon, four other ratings washed overboard. One of his petty officers was ill. The starboard diesel was still giving trouble. His one remaining torpedo was defective. The boat, which had no heating, was cold and damp, and everything – lockers, food, uniforms -was covered in a greenish-white mould. Feiler lay on his wet bunk, curled up against the cold, wincing at the irregular beat of the engine, and tried to sleep.

Up on the bridge, four men made up the night watch: one for each point of the compass. Cowled like monks in dripping black oilskins, lashed to the rail by metal belts, each had a pair of goggles and a pair of Zeiss binoculars clamped firmly to his eyes and was staring blindly into his own sector of darkness.

The cloud cover was ten-tenths. The wind was a steel attack. The hull of the U-boat thrashed beneath their feet with a violence that sent them skidding over the wet deck plates and knocking into one another.

Facing directly ahead, towards the invisible prow, was a young Obersteurmann, Heinz Theen. He was peering into such an infinity of blackness that it was possible to imagine they might have fallen off the edge of the world, when suddenly he saw a light. It flared out of nowhere, several hundred yards in front of him, winked for two seconds, then disappeared. If he hadn't had his binoculars trained precisely upon it, he would never have seen it.

Astonishing though it seemed, he realised he had just witnessed someone lighting a cigarette.

An Allied seaman lighting a cigarette in the middle of the North Atlantic.

He called down the conning tower for the captain.

By the time Feiler had scrambled up the slippery metal ladder to the bridge thirty seconds later the cloud had shifted slightly in the high wind and shapes were moving all around them. Feiler swivelled through 360 degrees and counted the outlines of nearly twenty

ships, the nearest no more than 500 yards away on the port side.

A whispered cry, as much of panic as command: 'Alarrrmm!'

The U-653 came out of her emergency dive and hung motionless in the calmer water beneath the waves.

Thirty-nine men crouched silently in the semidarkness listening to the sounds of the convoy passing overhead: the fast revs of the modern diesels, the ponderous churning of the steamers, the curious singing noises of the turbines in the warship escorts.

Feiler let them all go by. He waited two hours, then surfaced.

The convoy was already so far ahead as to be barely visible in the faint dawn light – just the masts of the ships and a few smudges of smoke on the horizon, and then, occasionally, when a high wave lifted the U-boat, the ironwork of bridges and funnels.

Feiler's task under standing orders was not to attack – impossible in any case, given his lack of torpedoes -but to keep his quarry in sight while drawing in every other U-boat within a radius of 100 miles.

'Convoy steering 070 degrees,' said Feiler. 'Naval grid square BD 1491.'

The first officer made a scrawled note in pencil then dropped down the conning tower to collect the Short Signal Code Book. In his cubbyhole next to the captain's berth the radioman pressed his switches. The Enigma came on with a hum.

2

At 7 a.m., Logie had sent Pinker, Proudfoot and Kingcome back to their digs to get some decent rest. 'Sod's law will now proceed to operate,' he predicted, as he watched them go, and sod's law duly did. Twenty-five minutes later, he was back in the Big Room with the queasy expression of guilty excitement which would characterise the whole of that day. 'It looks like it may have started.' St Erith, Scarborough and Flowerdown had all reported an E-bar signal followed by eight Morse letters, and within a minute one of the Wrens from the Registration Room was bringing in the first copies. Jericho placed his carefully in the centre of his trestle table.

RGHC DMIG. His heart began to accelerate. 'Hubertus net,' said Logie. '4601 kilocycles.' Cave was listening to someone on the telephone. He put his hand over the mouthpiece. 'Direction finders have a fix.' He clicked his fingers. 'Pencil. Quick.' Baxter threw him one. '49.4 degrees north,' he repeated. '38.8 degrees west. Got it. Well done.' He hung up.

Cave had spent all night plotting the convoys' courses on two large charts of the North Atlantic – one issued by the Admiralty, the other a captured German naval grid, on which the ocean was divided into thousands of tiny squares. The cryptanalysts gathered round him. Cave's finger came down on a spot almost exactly midway between Newfoundland and the British Isles. 'There she is. She's shadowing HX-229.' He made a cross on the map and wrote 0725 beside it.

Jericho said: 'What grid square is that?'

'BD1491.'

'And the convoy course?'

'070'

Jericho went back to his desk and in less than two minutes, using the Short Signal Code Book and the current Kriegsmarine address book for encoding naval grid squares ('Alfred Krause, Blucherplatz 15': Hut 8 had broken that just before the blackout) he had a five-letter crib to slide under the contact report.

R G H C D M I G

D D F G R X??

The first four letters announced that a convoy had been located steering 070 degrees, the next two gave the grid square, the final two represented the code name of the U-boat, which he didn't have. He circled R-D and D-R. A four-letter loop on the first signal.

i get D-R/R-D,' said Puck a few seconds later.

'So do I.'

'Me too,'said Baxter.

Jericho nodded and doodled his initials on the pad. 'A good omen.'

After that, the pace of events began to quicken.

At 8.25, two long signals were intercepted emanating from Magdeburg, which Cave at once surmised would be U-boat headquarters ordering every submarine in the North Atlantic into the attack zone; At 9.20, he put down the telephone to announce that the Admiralty had just signalled the convoy commander with a warning that he was probably being shadowed. Seven minutes later, the telephone rang again. Flowerdown intercept station. A second E-bar flash from almost the same location as the first. The Wrens hurried in with it: KLYS QNLP.

'The same hearse,' said Cave. 'Following standard operating procedure. Reporting every two hours, or near as damn it.'

'Grid square?'

'The same.'

'Convoy course?'

'Also the same. For now.'

Jericho went back to his desk and manipulated the original crib under the new cryptogram.

K L Y S Q N L P

D D F G R X??

Again, there were no letter clashes. The golden rule of Enigma, its single, fatal weakness: nothing is ever itself- A can never be A, B can never be B… It was working. His feet performed a little tap dance of delight beneath the table. He glanced up to find Baxter staring at him and he realised, to his horror, that he was smiling.

'Pleased?'

'Of course not.'

But such was his shame that when, an hour later, Logie came through to say that a second U-boat had just sent a contact signal, he felt himself personally responsible.

SOUY YTRQ

At 11.40, a third U-boat began to shadow the convoy, at 12.20, a fourth, and suddenly Jericho had seven signals on his desk. He was conscious of people coming up and looking over his shoulder – Logie with his burning hayrick of a pipe and the meaty smell and heavy breathing of Skynner. He didn't look round. He didn't talk. The outside world had melted for him. Even Claire was just a phantom now. There were only the loops of letters, forming and stretching out towards him from the grey Atlantic, multiplying on his sheets of paper, turning into thin chains of possibility in his mind.

They didn't stop for breakfast, nor for lunch. Minute by minute, throughout the afternoon, the cryptanalysts followed, at third hand, the progress of the chase two thousand miles away. The commander of the convoy was signalling to the Admiralty, the Admiralty had an open line to Cave, and Cave would shout each time a fresh development looked like affecting the hunt for cribs.

Two signals came at 13.40 – one a short contact report, the other longer, almost certainly originating from the U-boat that had started the hunt. Both were for the first time close enough to be fixed by direction finders on board the convoy's own escorts. Cave

listened gravely for a minute, then announced that HMS Mansfield, a destroyer, was being dispatched from the main body of merchantmen to attack the U-boats.

'The convoy's just made an emergency turn to the southeast. She's going to try to shake off the hearses while Mansfield forces them under.'

Jericho looked up. 'What course is she steering?'

'What course is she steering?' repeated Cave into the telephone. 'I said,' he yelled, 'what fucking course is she steering?' He winced at Jericho. The receiver was jammed tight to his scarred ear. 'All right. Yes. Thank you. Convoy steering 118 degrees.' Jericho reached for the Short Signal Code Book.

'Will they manage to get away?' asked Baxter.

Cave bent over his chart with a rule and protractor. 'Maybe. It's what I'd do in their place.'

A quarter of an hour passed and nothing happened.

'Perhaps they have done it,' said Puck. 'Then what do we do?'

Cave said: 'How much more material do you need?'

Jericho counted through the signals. 'We've got nine. We need another twenty. Another twenty-five would be better.'

'Jesus!' Cave regarded them with disgust. 'It's like sitting with a flock of carrion.'

Somewhere behind them a telephone managed half a ring before it was snatched out of its cradle. Logie came in a moment later, still writing.

'That was St Erith reporting an E-bar signal at 49.4 degrees north, 38.1 degrees west.'

'New location,' said Cave, studying his charts. He made a cross, then threw his pencil down and leaned back in his chair, rubbing his face. 'All she's managed to do is run straight from one hearse into another. Which is what? The fifth? Christ, the sea must be teeming with them.'

'She isn't going to get away,' said Puck, 'is she?'

'Not a chance. Not if they're coming in from all around her.'

A Wren moved among the cryptanalysts, doling out the latest cryptogram: BKEL UUXS.

Ten signals. Five U-boats in contact.

'Grid square?'said Jericho.

Hester Wallace was not a poker player, which was a mistake on her part as she had been blessed with a poker face that could have made her a fortune. Nobody watching her wheel her bicycle into the shed beside the canteen that afternoon, or seeing her flick her pass at the sentry, or squeezing up against the corridor wall in Hut 6 to let her march by, or sitting opposite her in Intercept Control – nobody would have guessed the turmoil in her mind.

Her complexion was, as ever, pale, her forehead slightly creased by a frown that discouraged conversation. She wore her long, dark hair like a headache, savagely twisted up and speared. Her costume was the usual uniform of the West Country schoolmistress: flat shoes, grey woollen stockings, plain grey skirt, white shirt and an elderly but well-cut tweed jacket which she would shortly take off and hang over the back of the chair, for the afternoon was warm. Her fingers moved across the blist in a short, staccato pecking motion. She had hardly slept all night.

Name of intercept station, time of interception, frequency, call sign, letter groups.

Where was the record of settings kept? That was the first matter to determine. Not in Control, obviously. Not in the Index Room. Not in the Registry. And not next door in the Registration Room, either: she had already made a quick inspection there. The Decoding Room was a possibility, but the Type-X girls were always complaining they were cramped for space, and sixty separate Enigma keys, their settings changed daily – in the case of the Luftwaffe, sometimes twice a day -well, that was a minimum of five hundred pieces of information every week, 25,000 in a year, and this was the war's fourth year. That would suggest a sizeable catalogue; a small library, in fact.

The only conclusion was that they had to be kept where the cryptanalysts worked, in the Machine Room, or else close by.

She finished blisting Chicksands, noon till three, and moved towards the door.

Her first pass through the Machine Room was spoiled by nerves: straight through it to the other end of the hut without even glancing from side to side. She stood outside the Decoding Room, cursing her fears, pretending to study the noticeboard. With a shaking hand she made a note about a performance of Die Fledermaus by the Bletchley Park Music Society which she had no intention of ever attending.

The second run was better.

There was no machinery in the Machine Room – the origin of its name was lost in the glorious mists of 1940 -just desks, cryptanalysts, wire baskets filled with signals and, on the wall to the right, shelf after shelf of files. She stopped and looked around distractedly, as if searching for a familiar face. The problem was, she knew nobody. But then her gaze fell upon a bald head with a few long, ginger hairs combed pathetically across a freckled crown, and she realised that wasn't entirely true.

She knew Cordingley.

Dear old, dull old Donald Cordingley, the winner – in a crowded field – of the Dullest Man in Bletchley contest. Ineligible for military service due to a funnel chest. By profession: actuary. Ten years' service with the Scottish Widows Assurance Society in the City of London, until a lucky third place in the Daily Telegraph crossword competition won him a seat in the Hut 6 Machine Room.

Her seat.

She watched him for a few more seconds, then moved away.

When she got back to Control Miles Mermagen was standing by her desk.

'How was Beaumanor?'

'Engrossing.'

She had left her jacket over her chair and he ran his hand over the collar, feeling the material between his thumb and forefinger, as if checking it for quality.

'How'd you get there?'

'A friend gave me a lift.'

'A male friend, I gather. Mermagen's smile was wide and unfriendly.

'How do you know that?' 'I have my spies,' he said.

The ocean was alive with signals. They were landing on Jericho's desk at the rate of one every twenty minutes.

At 16.00 a sixth U-boat fastened on to the convoy and soon afterwards Cave announced that HX-229 was making another turn, to 028 degrees, in her latest and (in his opinion) hopeless attempt to escape her pursuers.

By 18.00 Jericho had a pile of nineteen contact signals, out of which he had conjured three four-letter loops and a mass of half-sketched bombe menus that looked like the plans for some complex game of hopscotch. His neck and shoulders were so knotted with tension he could barely straighten up.

The room by now was crowded. Pinker, Kingcome and Proudfoot had come back on shift. The other British naval lieutenant, Villiers, was standing next to Cave, who was explaining something on one of his charts. A Wren with a tray offered Jericho a curling Spam sandwich and an enamel mug of tea and he took them gratefully.

Logie came up behind him and tousled his hair.

'How are you feeling, old love?'

'Wrecked, frankly.'

'Want to knock off?'

'Very funny.'

'Come into my office and I'll give you something. Bring your tea.'

The 'something' turned out to be a large, yellow Benzedrine tablet, of which Logie had half a dozen in an hexagonal pillbox.

Jericho hesitated. 'I'm not sure I should. These helped send me runny last time.'

'They'll get you through the night, though, won't they? Come on, old thing. The commandos swear by them.' He rattled the box under Jericho's nose. 'So you'll crash out at breakfast? So what? By then we'll either have this bugger beaten. Or not. In which case it won't matter, will it?' He took one of the pills and pressed it into Jericho's palm. 'Go on. I won't tell Nurse.' He closed Jericho's fingers around it and said quietly: 'Because I can't let you go, you know, old love. Not tonight. Not you. Some of the others, maybe, but not you.'

'Oh, Christ. Well, since you put it so nicely.'

Jericho swallowed the pill with a mouthful of tea. It left a foul taste and he drained his mug to try and swill it away. Logie regarded him fondly.

'That's my boy.' He put the box back in his desk drawer and locked it. 'I've been protecting your bloody back again, incidentally. I had to tell him you were much too important to be disturbed.'

Tell who? Skynner?'

'No. Not Skynner. Wigram.'

'What does he want?'

'You, old cock. I'd say he wants you. Skinned, stuffed and mounted on a pole somewhere. Really, I don't know, for such a quiet bloke, you don't half make some enemies. I told him to come back at midnight. All right by you?'

Before Jericho could reply the telephone rang and Logie grabbed it.

'Yes? Speaking.' He grunted and stretched across his desk for a pencil. 'Time of origin 19.02, 52.1 degrees north, 37.2 degrees west. Thanks, Bill. Keep the faith.'

He replaced the receiver.

'And then there were seven…"

It was dark again and the lights were on in the Big Room. The sentries outside were banging the blackout shutters into place, like prison warders locking up their charges for the night.

Jericho hadn't set foot out of the hut for twenty-four hours, hadn't even looked out of the window. As he slipped back into his seat and checked his coat to make sure the cryptograms were still there, he wondered vaguely what kind of day it had been and what Hester was doing.

Don't think about that now.

Already, he could feel the Benzedrine beginning to take effect. The muscles of his heart seemed feathery, his body charged. When he glanced across his notes, what had seemed inert and impenetrable a half-hour ago was suddenly fluid and full of possibility.

The new cryptogram was already on his desk: YALB DKYF.

'Naval grid square BD 2742,' called Cave. 'Course 055 degrees. Convoy speed nine and a half knots.'

Logie said: 'A message from Mr Skynner. A bottle of Scotch for the first man with a menu for the bombes.'

Twenty-three signals received. Seven U-boats in contact. Two hours to go till nightfall in the North Atlantic.

20.00: nine U-boats in contact.

20.46: ten.

The Control Room girls took a table near the serving hatch for their evening meal. Celia Davenport showed them all some pictures of her fiance, who was fighting in the desert, while Anthea Leigh-Delamere brayed endlessly about a meet of the Bicester Hunt. Hester passed on the photographs without looking at them. Her eyes were fixed on Donald Cordingley, queuing to collect his lump of coelacanth, or whatever other obscure example of God's aquatic creatures they were now required to eat.

She was cleverer than he, and he knew it.

She intimidated him.

Hello, Donald, she thought. Hello, Donald… Oh, nothing much, just this new back-break section, coming along with bucket and shovel after the Lord Mayor's parade… Now, listen, Donald, there's this funny little wireless net, Konotop-Prihiki-Poltava, in the southern Ukraine. Nothing vital, but we've never quite broken it and Archie – you must know Archie? – Archie has a theory it may be a variant on Vulture… Traffic runs through February and the first few days in March… That's right…

She watched him as he sat alone and picked at his lonely supper. She watched him, indeed, as if she were a vulture. And when, after fifteen minutes, he rose and scraped the leftovers from his plate into the swill bins, she rose as well, and followed him.

She was vaguely aware of the other girls staring after her in astonishment. She ignored them.

She tracked him all the way back to Hut 6, gave him five minutes to settle down, then went in after him.

The Machine Room was shaded and somnolent, like a library at dusk. She tapped him lightly on the shoulder.

'Hello, Donald.'

He turned round and blinked up at her in surprise. 'Oh, hello.' The effort of memory was heroic. 'Hello, Hester.'

'It's almost dark out there,' said Cave, looking at his watch. 'Not long now. How many have you had?'

'Twenty-nine,' said Baxter.

'I believe you said that would be enough, Mr Jericho?'

'Weather,' said Jericho, without looking up. 'We need a weather report from the convoy. Barometric pressure, cloud cover, cloud type, wind speed, temperature. Before it gets too dark.'

"They've got ten U-boats on their backs and you want them to tell you the weather?

'Yes, please. Fast as they can.'

The weather report arrived at 21.31.

There were no more contact signals after 21.40.

Thus convoy KX-229 at 22.00.

Thirty-seven merchant vessels, ranging in size from the 12,000-ton British tanker Southern Princess to the 3,500-ton American freighter Margaret Lykes, making slow progress through heavy seas, steering a course of 055 degrees, direct to England, lit up like a regatta by a full moon to a range of ten miles visibility – the first such night in the North Atlantic for weeks. Escort vessels: five, including two slow corvettes and two clapped out, elderly ex-American destroyers donated to Britain in 1940 in exchange for bases, one of which – HMS Mansfield – had lost touch with the convoy after charging down the U-boats because the convoy commander (on his first operational command) had forgotten to signal her with his second change of course. No rescue ship available. No air cover. No reinforcements within a thousand miles.

'All in all,' said Cave, lighting a cigarette and contemplating his charts, 'what you might fairly call a bit of a cock-up.'

The first torpedo hit at 22.01.

At 22.32, Tom Jericho was heard to say, very quietly, 'Yes.'

3

It was chucking-out time at the Eight Bells Inn on the Buckingham Road and Miss Jobey and Mr Bonnyman had virtually exhausted the main topic of their evening's conversation: what Bonnyman dramatically termed the 'police raid' on Mr Jericho's room.

They had heard the details at supper from Mrs Armstrong, her face still flushed with outrage at the memory of this violation of her territory. A uniformed officer had stood guard all afternoon on the doorstep ('in full view of the entire street, mind you'), while two plain-clothes men carrying a box of tools and waving a warrant had spent the best part of three hours searching;; the upstairs back bedroom, before leaving at teatime with a pile of books. They had dismantled the bed and the wardrobe, taken up the carpet and the floorboards, and brought down a heap of soot from the chimney. 'That young man is out,' declared Mrs Armstrong, folding her hamlike arms, 'and all rent forfeit.'

'"All rentforfeit"' repeated Bonnyman into his beer, for the sixth or seventh time. 'I love it.'

'And such a quiet man,' said Miss Jobey.

A handbell rang behind the bar and the lights flickered.

'Time, gentlemen! Time, please!'

Bonnyman finished his watery bitter, Miss Jobey her; port and lemon, and he escorted her unsteadily, past the dartboard and the hunting prints, towards the door.

The day that Jericho had missed had given the town its first real taste of spring. Out on the pavement the night air was still mild. Darkness touched the dreary street with romance. As the departing drinkers stumbled away into the blackout, Bonnyman playfully pulled Miss Jobey towards him. They fell back slightly into a doorway. Her mouth opened on his, she pressed herself up against him, and Bonnyman squeezed her waist in return. Whatever she might have lacked in beauty – and in the blackout, who could tell? – she more than made up for in ardour. Her strong and agile tongue, sweet with port, squirmed against his teeth.

Bonnyman, by profession a Post Office engineer, had been drafted to Bletchley, as Jericho had guessed, to service the bombes. Miss Jobey worked in the upstairs back bedroom of the mansion, filing Abwehr hand-ciphers. Neither, in accordance with regulations, had told the other what they did, a discretion which Bonnyman had extended somewhat to cover in addition the existence of a wife and two children at home in Dorking.

His hands slipped down her narrow thighs and began to hoist her skirt.

'Not here,' she said into his mouth, and brushed his fingers away.

Well (as Bonnyman would afterwards confide with a wink to the unsmiling police inspector who took his statement), the things a grown man has to do in wartime, and all for a simple you-know-what.

First, a cycle ride, which took them along a track and under a railway bridge. Then, by the thin beam of a torch, over a padlocked gate and through mud and brambles towards the hulk of a broken building. A great expanse of water somewhere close by. You couldn't see it, but you could hear the lapping in the breeze and the occasional cry of a waterfowl, and you could sense a deeper darkness, like a great black pit.

Complaints from Miss Jobey as she snagged her precious stockings and wrenched her ankle: loud and bitter imprecations against Mr Bonnyman and all his works which did not augur well for the purpose he had in mind. She started whining: 'Come on, Bonny, I'm frightened, let's go back.'

But Bonnyman had no intention of turning back. Even on a normal evening, Mrs Armstrong monitored every peep and squeak in the ether of the Commercial Guesthouse like a one-woman intercept station; tonight, she'd be on even higher alert than usual. Besides, he always found this place exciting. The light flashed on bare brick and on evidence of earlier liaisons – AE + GS, Tony = Kath. The spot held an odd erotic charge. So much had clearly happened here, so many whispered fumblings… They were a part of a great flux of yearning that went back long before them and would go on long after them – illicit, irrepressible, eternal. This was life. Such, at any rate, were Bonnyman's thoughts, although naturally he didn't express them at the time, nor afterwards to the police.

'And what happened next, sir? Precisely.'

He won't admit to this either, thank you very much, precisely or imprecisely.

But what did happen next was that Bonnyman wedged the torch in a gap in the brickwork where something had been torn from the wall, and threw his arms around Miss Jobey. He encountered a little light resistance at first – some token twisting and turning and 'stop it', 'not here' – which quickly became less convincing, until suddenly her tongue was up to its tricks again and they were back where they'd left off outside the Eight Bells Inn. Once again his hands began to ride up her skirt and once again she pushed him away, but this time for a different reason. Frowning slightly, she ducked and pulled down her knickers. One step, two steps, and they had vanished into her pocket. Bonnyman watched, enraptured.

'What happened next, inspector, precisely, is that Miss Jobey and myself noticed some hessian sacking in the corner.'

She with her skirt up above her knees, he with his trousers down around his ankles, shuffling forwards like a man in leg-irons, dropping heavily to his knees, a cloud of dust from the sacks rising and blossoming in the torch-beam, then much squirming and complaining on her part that something was digging into her back.

They stood and pulled away the sacks to make a better bed.

'And that was when you found it?'

'That was when we found it.'

The police inspector suddenly brought his fist down hard on the rough wooden table and shouted for his sergeant.

'Any sign of Mr Wigram yet?'

'We're still looking, sir.'

'Well, bloody well find him, man. Find him.'

4

The bombe was heavy – Jericho guessed it must weigh more than half a ton – and even though it was mounted on castors it still took all his strength, combined with the engineer's, to drag it away from the wall. Jericho pulled while the engineer went behind it and put his shoulder to the frame to heave. It came away at last with a screech and the Wrens moved in to strip it.

The decryptor was a monster, like something out of an H. G. Wells fantasy of the future: a black metal cabinet, eight feet wide and six feet tall, with scores oft five-inch-diameter drum wheels set into the front. The back was hinged and opened up to show a bulging mass of coloured cables and the dull gleam of metal drums. In the place where it had stood on the concrete floor there was a large puddle of oil.

Jericho wiped his hands on a rag and retreated to watch from a corner. Elsewhere in the hut a score of other bombes were churning away on other Enigma keys and the noise and the heat were how he imagined a ship's engine room might be. One Wren went round to the back of the cabinet and began disconnecting and replugging the cables. The other moved along the front, pulling out each drum in turn and checking it. Whenever she found a fault in the wiring she would hand the drum to the engineer who would stroke the tiny brush wires back into place with a pair of tweezers. The contact brushes were always fraying, just as the belt which connected the mechanism to the big electric motor had a tendency to stretch and slip whenever there was a heavy load. And the engineers had never quite got the earthing right, so that the cabinets had a tendency to give off powerful electric shocks.

Jericho thought it was the worst job of all. A pig of a job. Eight hours a day, six days a week, cooped up in this windowless, deafening cell. He turned away to look at his watch. He didn't want them to see his impatience. It was nearly half past eleven.

His menu was at that moment being rushed into bombe bays all across the Bletchley area. Eight miles north of the Park, in a hut in a clearing in the forested estate of Gayhurst Manor, a clutch of tired Wrens near the end of their shift were being ordered to halt the three bombes running on Nuthatch (Berlin-Vienna-Belgrade Army administration), strip them and prepare them for Shark. In the stable block of Adstock Manor, ten miles to the west, the girls were actually sprawled with their feet up beside their silent machines, drinking Ovaltine and listening to Tommy Dorsey on the BBC Light Programme, when the supervisor came storming through with a sheaf of menus and told them to stir themselves, fast. And at Wavendon Manor, three miles northeast, a similar story: four bombes in a dank and windowless bunker were abruptly pulled off Osprey (the low-priority Enigma key of the Organisation Todt) and their operators told to stand by for a rush job.

Those, plus the two machines in Bletchley's Hut 11, made up the promised dozen bombes.

The mechanical check completed, the Wren went back to the first row of drums and began adjusting them to the combination listed on the menus. She called out the letters to the other girl, who checked them.

'Freddy, Butter, Quagga…'

'Yes.'

'Apple, X-ray, Edward

'Yes.'

The drums slipped on to their spindles and were fixed into place with a loud metallic click. Each was wired to mimic the action of a single Enigma rotor: 108 in all, equivalent to thirty-six Enigma machines running in parallel. When all the drums had been set, the bombe was trundled back into place and the motor started.

The drums began to turn, all except one in the top row which had jammed. The engineer gave it a whack with his spanner and it, too, began to revolve. The bombe would now run continuously on this menu – certainly for one day; possibly, according to Jericho's calculations, for two or three – stopping occasionally when the drums were so aligned they completed a circuit. Then the readings on the drums would be checked and tested, the machine restarted, and so it would go on until the precise combination of settings had been found, at which point the cryptanalysts would be able to read that day's Shark traffic. Such, at any rate, was the theory.

The engineer began dragging out the other bombe and Jericho moved forward to help, but was stopped by a tugging on his arm.

'Come on, old love,' shouted Logie above the din.

'There's nothing more we can do here.' He pulled at his sleeve again.

Reluctantly, Jericho turned and followed him out of the hut.

He felt no sense of elation. Maybe tomorrow evening or maybe on Thursday, the bombes would give them the Enigma settings for the day now ending. Then the real work would begin – the laborious business of trying to reconstruct the new Short Weather Code Book – taking the meteorological data from the convoy, matching it to the weather signals already received from the surrounding U-boats, making some guesses, testing them, constructing a fresh set of cribs… It never ended, this battle against Enigma. It was a chess tournament of a thousand rounds against a player of prodigious defensive strength, and each day the pieces went back to their original positions and the game began afresh.

Logie, too, seemed rather flat as they walked along the asphalt path towards Hut 8.

'I've sent the others home to their digs for some kip,' he was saying, 'which is where I'm going. And where you ought to go, too, if you're not too high to sleep.'

I'll just clear up here for a bit, if that's all right. Take the code book back to the safe.'

'Do that. Thanks.'

'And then I suppose I'd better face Wigram.'

'Ah, yes. Wigram.'

They went into the hut. In his office, Logie tossed Jericho the keys to the Black Museum. 'And your prize,' he said, holding up a half-bottle of scotch. 'Don't let's forget that.'

Jericho smiled. 'I thought you said Skynner was offering a full bottle.'

'Ah, well, yes, I did, but you know Skynner.'

'Give it to the others.'

'Oh, don't be so bloody pious.' From the same drawer Logie produced a couple of enamel mugs. He blew away some dust and wiped their insides with his forefinger. 'What shall we drink to? You don't mind if I join you?'

'The end of Shark? The future?'

Logie splashed a large measure of whisky into each mug. 'How about,' he said, shrewdly, offering one to Jericho, 'how about your future?'

They clinked mugs.

'My future.'

They sat in their overcoats, in silence, drinking.

'I'm defeated,' said Logie at last, using the desk to pull himself to his feet. 'I couldn't tell you the year, old love, never mind the day.' He had three pipes in a rack and he blew noisily through each of them, making a harsh, cracking sound, then slipped them into his pocket. 'Now don't forget your scotch.'

'I don't want the bloody scotch.'

'Take it. Please. For my sake.'

In the corridor, he shook Jericho's hand, and Jericho feared Logie was going to say something embarrassing. But whatever it was he had in mind, he thought better of it. Instead, he merely gave a rueful salute and lurched along the passage, banging the door behind him.

The Big Room, in anticipation of the midnight shift, was almost empty. A little desultory work was being done on Dolphin and Porpoise at the far end. Two young women in overalls were on their knees around Jericho's desk, gathering every scrap of waste paper into a couple of sacks, ready for incineration. Only Cave was still there, bent over his charts. He looked up as Jericho came in.

'Well? How's it going for you?'

'Too early to tell,' said Jericho. He found the code book and slipped it into his pocket. 'And you?'

'Three hit so far. A Norwegian freighter and a Dutch cargo ship. They just went straight to the bottom. The third's on fire and going round and round in circles. Half the crew lost, the other half trying to save her.'

'What is she?'

'American Liberty ship. The James Oglethorpe. Seven thousand tons, carrying steel and cotton.'

'American,' repeated Jericho. He thought of Kramer.

'My brother died, one of the first'

'It's a slaughter,' said Cave, 'an absolute bloody slaughter. And shall I tell you the worst of it? It's not going to finish tonight. It's going to go on and on like this for days. They're going to be chased and harried and torpedoed right the way across the bloody North Atlantic. Can you imagine what that feels like? Watching the ship next to you blow up? Not being allowed to stop and search for survivors? Waiting for your turn?' He touched his scar, then seemed to realise what he was doing and let his hand fall. There was a terrible resignation in the gesture. 'And now, apparently, they're picking up U-boat signals swarming all around SC-122.'

His telephone began to ring and he swung away to answer it. While his back was turned, Jericho quietly placed the half-empty half-bottle of scotch on his desk, then made his way out into the night.

His mind, on a fuel of Benzedrine and scotch, seemed to be wheeling away on a course of its own, churning like the bombes in Hut 11, making bizarre and random connections – Claire and Hester and Skynner, and Wigram with his shoulder holster, and the tyre tracks in the frost outside the cottage, and the blazing Liberty ship going round and round over the bodies of half her crew.

He stopped by the lake to breathe some fresh air and thought of all the other occasions when he had stood here in the darkness, gazing at the faint silhouette of the mansion against the stars. He half-closed his eyes and saw it as it might have been before the war. A midsummer evening. The sounds of an orchestra and a bubble of voices drifting across the lawn. A line of Chinese lanterns, pink and mauve and lemon, stirring in the arboretum. Chandeliers in the ballroom. White crystal fracturing on the smooth surface of the lake.

The vision was so strong that he found he was sweating in his overcoat against the imagined heat, and as he climbed the slope towards the big house he fancied he saw a line of silver Rolls-Royces, their chauffeurs leaning against the long bonnets. But as he drew closer he saw that the cars were merely buses, come to drop off the next shift, pick up the last, and that the music in the mansion was only the percussion of telephone bells and the tapping of hurrying footsteps on the stone floor.

In the labyrinth of the house he nodded cautiously to the few people he passed – an elderly man in a dark grey suit, an Army captain, a WAAF. They appeared seedy in the dingy light and he guessed, by their expressions, he must look pretty odd himself. Benzedrine could do funny things to the pupils of your eyes, he seemed to remember, and he hadn't shaved or changed his clothes for more than forty hours. But nobody in Bletchley was ever thrown out for simply looking strange, or the place would have been empty from the start. There was old Dilly Knox, who used to come to work in his dressing gown, and Turing who cycled in wearing a gas mask to try to cure his hay fever, and the cryptanalyst from the Japanese section who had bathed naked in the lake one lunchtime. By comparison, Jericho was as conventional as an accountant.

He opened the door to the cellar passage. The bulb must have blown since his last visit and he found himself peering into a darkness as chill and black as a catacomb. Something gleamed very faintly at the foot of the stairs and he groped his way down the steps towards it. It was the keyhole to the Black Museum, traced in luminous paint: a trick they had learned in the Blitz.

Inside the room the light switch worked. He unlocked the safe and replaced the code book and for a moment he was seized by the crazy notion of hiding the stolen cryptograms inside it as well. Folded into an envelope they might pass unnoticed for months. But when, after tonight, was he likely to pass this way again? And one day they would be discovered. And then all it would take would be a telephone call to Beaumanor and everything would be unravelled – his involvement, Hester's…

No, no.

He closed the steel door.

But still he couldn't quite bring himself to leave. So much of his life was here. He touched the safe and then the rough, dry walls. He drew his finger through the dust on the table. He contemplated the row of Enigmas on the metal shelf. They were all encased in light wood, mostly in their original German boxes, and even in repose they seemed to exude a compelling, almost menacing power. These were far more than mere machines, he thought. These were the synapses of the enemy's brain – mysterious, complex, animate.

He stared at them for a couple of minutes, then began to turn away.

He stopped himself.

'Tom Jericho,' he whispered. 'You bloody fool.'

The first two Enigmas he lifted down and inspected turned out to be badly damaged and unusable. The third had a luggage label attached to its handle by a bit of string: 'Sidi Bou Zid 14/2/43'. An Afrika Korps Enigma, captured by the Eighth Army during their

attack on Rommel last month. He laid it carefully on the table and unfastened the metal clasps. The lid opened easily.

This one was in perfect condition: a beauty. The letters on the keys were unworn, the black metal casing unscratched, the glass bulbs clear and gleaming. The three rotors – stopped, he saw, at ZDE – glinted silver beneath the naked light. He stroked it tenderly. It must only just have left its makers. 'Chiffreirmaschine Gesellschaft,' read their label. 'Heimsoeth und Rinke, Berlin-Wilmersdorf, Uhlandstrasse 138.'

He pushed a key. It was stiffer than on a normal typewriter. When he had depressed it far enough, the machine emitted a clunk and the right-hand rotor moved on a notch. At the same time, one of the bulbs lit Up.

Hallelujah!

The battery was charged. The Enigma was live.

He checked the mechanism. He stooped and typed C. The letter J lit up. He typed L and got a U. A, I, R and E yielded, successively, X, P, Q and Q again.

He lifted the Enigma's inner lid and detached the spindle, set the rotors back at ZDE and locked them into place. He typed the cryptogram JUXPQQ and C-L-A-I-R-E was spelled out letter by letter on the bulbs in little bursts of light.

He fumbled through his pockets for his watch. Two minutes to twelve.

He folded the lid back into place and hoisted the Enigma up on its shelf. He made sure to lock the door behind him.

To the people whom he ran past in the mansion's corridors, who was he? Nothing. Nobody. Just another peculiar cryptanalyst in a flap.

Hester Wallace, as agreed, was in the telephone box at midnight, the receiver in her hand, feeling more foolish than afraid as she pretended to make a call. Beyond the glass, two currents of pale sparks were flowing quietly in the dark, as one shift streamed in from the main gate and the other ebbed towards it. In her pocket was a sheet of Bletchley's wood-flecked, brownish notepaper on which were jotted six entries.

Cordingley had swallowed her story whole – indeed, he had been, if anything, a little too eager to help. Unable at first to locate the relevant file, he had called in aid a pimply, jug-eared youth with wispy yellow hair. Could this child, she had wondered, this foetus-face, really be a cryptanalyst? But Donald had whispered yes, he was one of the best: now the professions and the universities had all been picked over, they were turning to boys straight out of school. Unformed. Unquestioning. The new elite.

The file had been procured, a space cleared in a corner, and never had Miss Wallace made a pencil move more quickly. The worst part had been at the end: keeping her nerve and not fleeing when she'd finished, but checking the figures, returning the file to the Foetus, and observing the normal social code with Donald

'We really must have a drink one of these evenings.'

'Yes really we must.'

'I'll be in touch, then.'

'Absolutely. So shall I.'

Neither, of course, having the slightest intention of ever doing so.

Come on, Tom Jericho.

Midnight passed. The first of the buses lumbered by – invisible, almost, except for its exhaust fumes, which made a puff of pink cloud in its red rear lights.

And then, just as she was beginning to give up hope, a blur of white. A hand tapped softly on the glass. She dropped the telephone and shone her torch on to the face of a lunatic pressed close to the pane. Dark wild eyes and a convict mask of shadowed beard. 'There's really no need to scare me half to death,' she muttered, but that was in the privacy of the phone booth. As she came out, all she said was: I've left your numbers on the telephone.'

She held the door open for him. His hand rested on hers. A brief moment of pressure signalled his thanks – too brief for her to tell whose fingers were the coldest.

'Meet me here at five.'

Exhilaration gave a fresh energy to her tired legs as she pedalled up the hill away from Bletchley.

He needed to see her at five. How else could one interpret that, except as meaning he had found a way? A victory! A victory against the Mermagens and the Cordingleys!

The gradient steepened. She rose to tread the pedals. The bicycle waved from side to side like a metronome. The light danced on the road.

Afterwards, she was to reproach herself severely for this premature jubilation, but the truth was she would probably never have seen them anyway. They had positioned themselves quite carefully, drawn up parallel with the track and hidden by the hawthorn hedge – a professional job – so that when she came round the corner and began to bounce over the potholes towards the cottage she passed them in the shadows without a glance.

She was six feet from the door when the headlights came on – slitted blackout headlights,, but dazzling enough to splash her shadow against the whitewashed wall. She heard the engine cough and turned, shielding her eyes, to see the big car coming at her – calm, unhurried, implacable, nodding over the bumpy ground.

5

Jericho told himself to take his time. There's no hurry. You've given yourself five hours. Use them.

He locked himself into the cellar room, leaving the key half turned in the keyhole, so that anyone trying to insert their key from the other side would find it blocked. He knew he'd have to open up eventually – otherwise, what was he? Just a rat in a trap. But at least he would now have thirty seconds' warning, and to give himself a cover story, he reopened the Naval Section safe and spread the handful of maps and code books across the narrow table. To these he added the stolen cryptograms and key settings, and his watch, which he placed before him with its lid open. Like preparing for an examination, he thought. 'Candidates must write on one side of the paper only; this margin to be left blank for the use of the examiner.'

Then he lifted down the Enigma and removed the cover.

He listened. Nothing. A dripping pipe somewhere, that was all. The walls bulged with the pressure of the cold earth; he could smell the soil, taste the spores of damp lime plaster. He breathed on his fingers and flexed them.

He would work backwards, he decided, deciphering the last cryptogram first, on the theory that whatever had caused Claire's disappearance was contained somewhere in those final messages.

He ran his fingers down the columns of notation to find the Vulture settings for 4 March – panic day in the Bletchley Registry.

III V IV GAH CX AZ DV KT HU LW GP EY MR FQ

The Roman numerals told him which three out of the machine's five rotors were to be used that day, and what order they were to be placed in. GAH gave him the rotor starting positions. The next ten letter pairs represented the cross-pluggings he needed to make on the plugboard at the back of the Enigma. Six letters were left unconnected which, by some mysterious and glorious fold in the laws of statistics, actually increased the number of potential different cross-pluggings from almost 8 million million (25 x 23x21x 19 x 17 x 15 x 13 x 11 x 9 x 7 x 5 x 3) to more than 150 million million.

He did the plugging first. Short lengths, of corded, chocolate-coloured flex, tipped at either end by brass plugs sheathed in bakelite that sank with satisfying precision into the lettered sockets: C to X, A to Z…

Next he lifted the Enigma's inner lid, unlocked the spindle, and slid off the three rotors that were already loaded. From a separate compartment he withdrew the two spares.

Each rotor was the size and thickness of an ice-hockey puck, but heavier: a code wheel with twenty-six terminals – pin-shaped and spring-loaded on one side, flat and circular on the other – with the letters of the alphabet engraved around the edge. As the rotors turned against one another, so the shape of the electrical circuit they completed varied. The right-hand rotor always moved on a letter each time a key was struck. Once every twenty-six letters, a notch in its alphabet ring caused the middle rotor also to move on a place. And when, eventually, the middle rotor reached its turnover position, the third rotor would move. Two rotors moving together was known at Bletchley as a crab; three was a lobster.

He sorted the rotors into the order of the day – III, V and IV – and slipped them on to the spindle. He twirled III and set it at the letter G, V at A and IV at H, and closed the lid.

The machine was now primed just as its twin had been in Smolensk on the evening of 4 March.

He touched the keys. He was ready.

The Enigma worked on a simple principle. If, when the machine was set in a particular way, pressing key A completed a circuit that illuminated bulb X, then it followed – because electric current is reciprocal – that, in the same position, pressing key X would illuminate bulb A. Decoding was designed to be as easy as encoding.

Jericho realised quite quickly that something was going wrong. He would type a letter of the cryptogram with his left index finger and with his right hand make a note of the character illuminated on the display panel. T gave him H, R gave him Y, X gave him C… This was no German he recognised. Still, he went on in the increasingly desperate hope it would start to come right. Only after forty-seven letters did he give up.

HYCYKWPIOROKDZENAJEWICZJPTAKJHRUTBPYSJMOTYLPCIE

He ran his hands through his hair.

Sometimes an Enigma operator would insert meaningless padding around proper words to disguise the sense of his message, but never this much, surely? There were no proper words that he could discern hidden anywhere in this gibberish.

He groaned, leaned back in his chair and stared at the flaking plaster ceiling.

Two possibilities, each equally unpleasant.

One: the message had been super-enciphered, its plaintext scrambled once, and then again to make its meaning doubly obscure. A time-consuming technique, usually reserved for only the most secret communications.

Two: Hester had made a mistake in transcription – had got, perhaps, just one letter wrong – in which case he could sit here, literally for the rest of his life, and still he would never make the cryptogram disgorge its secrets.

Of the two explanations, the latter was the more likely.

He paced around his cell for a while, trying to get some circulation back into his legs and arms. Then he set the rotors back at GAH and made an attempt to decipher the second message from 4 March. The same result:

SZULCJK UKAH

He didn't even bother with the third and fourth but instead played around with the rotor settings – GEH, CAN, CAH – in the hope she might simply have got one letter wrong, but all the Enigma winked at him was more gobbledygook.

Four in the car. Hester in the back seat next to Wigram. Two men in the front. The doors all locked, the heater on, a stench of cigarette smoke and sweat so strong that Wigram had his paisley scarf pressed delicately to his nose. He kept his face half-turned from her all journey and didn't say a word until they reached the main road. Then they pulled across the white lines to overtake another car and their driver switched on a police bell.

'Oh, for Christ's sake, Leveret, cut it out.'

The noise stopped. The car swerved left, then right. They jolted down a rutted track and Hester's fingers sank deeper into the leather upholstery as she strained to avoid toppling into Wigram. She hadn't spoken, either – it was her single, token gesture of defiance, this silence. She was damned if she was going to show her nerves by babbling like a girl.

After a couple of minutes they stopped somewhere and Wigram sat motionless, a statesman, while his men in the front seats scrambled out. One of them opened his door. Torches flashed in the darkness. Shadows appeared. A welcoming committee.

'Got those lights up yet, inspector?' asked Wigram.

'Yes, sir.' A deep male voice; a Midlands accent. 'A lot of complaints from the air raid people, though.'

'Well, they can frig off for a start. Jerry wants to bomb this place, he's welcome. Got the plans?'

'Yes, sir.'

'Good-oh.' Wigram grabbed the roof and hoisted himself out on the running board. He waited a second or two and when Hester didn't move he ducked back inside and flexed his fingers irritably. 'Come on, come on. D'you expect me to carry you?'

She slid across the seat.

Two other cars – no, three other cars with their headlights on, showing the cut-out patterns of men moving, plus a small Army truck and an ambulance. It was the ambulance that shook her. Its doors were open and, as Wigram guided her past it, his hand lightly on her elbow, she caught the smell of disinfectant, saw the dun-coloured oxygen cylinders, the stretchers with their coarse brown blankets, their leather straps, their innocent white sheets. Two men sat on the rear bumper, legs outstretched, smoking. They stared at her without interest.

'Been here before?' said Wigram.

'Where are we?'

'Lovers' lane. Not your scene, I fancy.'

He was holding a flashlight and as he stood aside to usher her through a gate she saw a sign: DANGER: FLOODED CLAY PIT – VERY DEEP WATER. She could hear a guttural engine somewhere ahead, and the cry of sea-birds. She started to shake.

'The hand of the Lord was upon me, and carried me out in the spirit of the Lord, and set me down in the midst of the valley which was full of bones.'

'D'you say something?' asked Wigram.

'I don't believe so.'

Oh, Claire, Claire, Claire…

The engine noise was louder now, and seemed to be coming from inside a brick building to her left. A faint white light shone up through the gaps in its roof to reveal a tall, square chimney, its lower part engulfed by ivy. She was vaguely aware that they were at the head of a procession. Behind them came the driver, Leveret, and then the second man from the car wearing a belted gaberdine, and then the police inspector.

'Mind yourself here,' warned Wigram, and he tried to take her arm again but she shook him off. She picked her own way between the clumps of brick and the towering weeds, heard voices, turned a corner, and was confronted by a dazzling line of arc lights illuminating a broad path. Six policemen were working their way ' along it, in parallel, on their hands and knees among a glitter of broken glass and rubble. Behind them, one soldier tended a shuddering generator; another unreeled a drum of cable; a third was rigging more lights.

Wigram grinned and winked at her, as if to say: See what I can command. He was pulling on a pair of light brown, calfskin gloves. 'Got something to show you.' In a corner of the building, a police sergeant stood beside a rumpled heap of sacks. Hester had to will her legs to move forwards. Please, Lord, don't let it be her,

'Get your notebook out,' said Wigram to the sergeant. He hoisted the tails of his overcoat and squatted on his haunches. 'I am showing the witness, first, one lady's coat, ankle-length by the look of it, colour grey, trimmed with black velvet.' He drew it completely out of the sack and turned it over. 'Grey satin lining. Quite badly stained. Probably blood. Need to check it. Collar label: "Hunters, Burlington Arcade". And the witness responded?' He held it up, without looking round.

Remember, I said, 'That's too beautiful to put on every day,' and you said, 'Silly old Hester, that's the only reason there is to wear it'?

'And the witness responded?.'

'It's hers.'

'"It's hers."' Got that? Good. OK. Next. One lady's shoe. Left foot. Black. High heel. Heel snapped off. Hers, d'you think?'

'How can I tell? One shoe -'

'Largish. Say, size seven. Eight. What size did she take?' A pause, then Hester, quietly: 'Seven.'

'We've found the other one outside, sir,' said the inspector. 'Near the water's edge.'

'And a pair of knickers. White. Silk. Badly bloodstained.' He held them out at arm's length between finger and thumb. 'Recognise these, Miss Wallace?' He let them drop and rummaged in the bottom of the sack. 'Final item. One brick.' He shone his flashlight onto it; something glinted. 'Also bloodstained. Blonde hairs attached.'

'Eleven main buildings,' said the inspector. 'Eight of them with kilns, four with chimneys still standing. Rail spur here with sidings, linking into the main line, and a branch going off here, right through the site.'

They were outside now, at the spot where the second shoe had been found, and the map was spread over a rusting water rank. Hester stood away from them, Leveret watching her, his hands hanging loosely by his sides. There were more men moving down by the water's edge, torches stabbing the night.

'Local fishing club use a shed here, near the jetty. Three rowing boats usually stored.'

'Usually?'

'Door's been kicked in, sir. Season's over. That's why nobody discovered it. A boat's missing."

'Since?'

'Well, there was some fishing on Sunday. Deep ledgering for carp. That was the last day of the season. Everything was all right then. So any time from Sunday night onwards.'

'Sunday. And we're now into Wednesday.' Wigram sighed and shook his head.

The inspector spread his hands. 'With respect, sir, I have three men stationed in Bletchley. Bedford lent us six, Buckingham nine. We're two miles from the centre of town. There is a limit. Sir.'

Wigram didn't seem to hear him. 'And how big's the lake?'

'About a quarter of a mile across.'

'Deep?'

'Yes, sir.'

'What – twenty, thirty feet?'

'At the edges. Shelving to sixty. Could be seventy. It's an old working. They built the town with what they dug out here.'

'Did they really?' Wigram flashed his light across the lake. 'Makes sense, I suppose. Making one hole out of another.' Mist was rising, swirling in the breeze like steam above a cauldron. He swung the beam round and pointed it back at the building. 'So what happened here?' he said softly. 'Our man lures her out for a shag on Sunday night. Kills her, probably with that brick. Drags her down here…' The beam traced the path from the kilns to the water. 'Strong man – must have been, she was a big girl. Then what? Gets a boat. Stuffs the body in a sack maybe. Weights it with bricks. That's obvious. Rows it out. Dumps it. A muffled splash at midnight, just like in the pictures… He probably meant to come back for the clothes as well, but something put him off. Perhaps the next pair of lovebirds had already arrived.' He played the light over the mist again. 'Seventy feet deep. Frigging hell! We'll need to put a submarine down there to find her.'

'May I go now?' said Hester. She had kept herself very quiet and composed so far, but now the tears had started and she was drawing in great gulps of air.

Wigram aimed the beam at her wet face. 'No,' he said sadly. 'I'm rather afraid you can't.'

Jericho was replugging the cipher machine as quickly as his numb fingers would permit him.

Enigma settings for German Army key Vulture, 6 February 1943:

I V III DMR EY JL AK NV FZ CT HP MX BQ GS

The final four cryptograms were hopeless, a disaster, mere chaos out of chaos. He had wasted too much time on them already. He would begin again, this time with the first signal. E to Y, J to L. And if this didn't work? Don't even think it. A to K, N to V… He lifted the lid, unfastened the spindle, slid off the rotors. Above his head, the great house was silent. He was too deeply entombed to hear a footstep. He wondered what they were doing up there. Looking for him? Probably. And if they woke up Logie it wouldn't take them long to find him. He slid the rotors into place – first, fifth, third – and clicked them round to DMR.

Almost at once he began to sense success. First C and X, which were nulls, and then A, N, O, K, H.

An OKH…

To OKH. Oberkommando des Heeres. The High Command of the Army.

A miracle.

His finger hammered away at the key. The lights flashed.

An OKH/BEFEHL To the office of the Commander-in-Chief.

Dringend.

Urgent.

Melde Auffindung zahlreicher menschlicher Uberreste zwolfKm westlich Smolensk…

Discovered yesterday twelve kilometres west Smolensk human remains…

Hester was locked in the car with Wigram, Leveret standing guard outside.

Jericho. He was asking her about Jericho. Where was he? What was he doing? When did she last see him?

'He's left the hut. He's not at his digs. He's not at the cottage. I ask you: Where the hell else is there to go in this frigging town?'

She said nothing.

He tried shouting at her, pounding his fist on the seat in front, and then, when that didn't work, he gave her his handkerchief and tried sympathy, but the scent of cologne on the silk and the memory of the blonde hair gilding the brick made her want to be sick and he had to wind his window down and get Leveret to come round and open her door.

'They've found the boat, sir,' said Leveret. 'Blood in the bottom.'

Just before three o'clock, Jericho had the first message deciphered.

TO THE OFFICE OF THE COMMANDER IN CHIEF. URGENT. DISCOVERED TWELVE KILOMETRES WEST SMOLENSK EVIDENCE HUMAN REMAINS. BELIEVED EXTENSIVE, POSSIBLY THOUSANDS. HOW AM I TO PROCEED? LACHMAN, OBERST, FIELD POLICE.

Jericho sat back and contemplated this marvel. Well, yes, Herr Oberst, how are you to proceed? I die to know.

Once again he began the tedious procedure of replugging and re-rotoring the Enigma. The next signal had been sent from Smolensk three days later, on 9 February. A, N, O, K, H, B, E, F, E, H, L… The exquisite formality of the German armed forces unfolded before him. And then a null, and then G, E, S, T, E, R, N, U, N, D, H, E, U, T, E.

Gestern und heute. Yesterday and today.

And so on, letter by letter, inescapably, remorselessly – press, clunk, light, note – stopping occasionally to massage his fingers and straighten his back, the whole ghastly story made worse by the slowness with which he had to read it, his eyeballs pressed to the crime. Some of the words gave him difficulty. What was mumifizierfi Could it be 'mummified'? And Sagemehl geknebelti 'Gagged with sawdust'?

PRELIMINARY EXCAVATION UNDERTAKEN IN FOREST NORTH DNIEPER CASTLE YESTERDAY AND TODAY. SITE APPROXIMATELY TWO HUNDRED SQUARE METRES. TOPSOIL COVERING TO DEPTH OF ONE POINT FIVE METRES PLANTED PINE SAPLINGS. FIVE LAYERS CORPSES. UPPER MUMMIFIED LOWER LIQUID. TWENTY BODIES RECOVERED. DEATH CAUSED BY SINGLE SHOT HEAD. HANDS BOUND WIRE. MOUTHS GAGGED CLOTH AND SAWDUST. MILITARY UNIFORMS, HIGH BOOTS AND MEDALS INDICATE VICTIMS POLISH OFFICERS. SEVERE FROST AND HEAVY SNOWFALL OBLIGE US SUSPEND OPERATIONS PENDING THAW. I SHALL CONTINUE MY INVESTIGATIONS. LACHMAN, OBERST, FIELD POLICE.

Jericho took a tour around his little cell, flapping his arms and stamping his feet. It seemed to him to be peopled with ghosts, grinning at him with toothless mouths blasted into the backs of their heads. He was walking in the forest himself. The cold sliced his flesh. And when he stopped and listened he could hear the sound of trees being uprooted, of spades and pickaxes ringing on frozen earth.

Polish officers?

Puck?

The third signal, after a gap of eleven days, had been sent on 20th February. Nach Eintreten 'Tauwetter Exhumierungen im Wald bei Katyn fortgesetzt…

FOLLOWING THAW KATYN FOREST EXCAVATIONS RESUMED EIGHT HUNDRED YESTERDAY. FIFTY-TWO CORPSES EXAMINED. QUANTITIES OF PERSONAL LETTERS, MEDALS, POLISH CURRENCY RECOVERED. ALSO SPENT PISTOL CARTRIDGE CASES SEVEN POINT SIX FIVE MILLIMETRE STAMPED QUOTE GECO D UNQUOTE. INTERROGATION LOCAL POPULATION ESTABLISHES ONE EXECUTIONS CONDUCTED NKVD DURING SOVIET OCCUPATION MARCH AND APRIL NINETEEN HUNDRED AND FORTY. TWO VICTIMS BELIEVED BROUGHT FROM KOZIELSK DETENTION CAMP BY RAIL TO GNIEZDOVO STATION TAKEN INTO FOREST AT NIGHT IN GROUPS ONE HUNDRED SHOTS HEARD. THREE TOTAL NUMBER VICTIMS ESTIMATED TEN THOUSAND REPEAT TEN THOUSAND. ASSISTANCE URGENTLY REQUIRED IF FURTHER EXCAVATION DESIRED.

Jericho sat motionless for fifteen minutes, gazing at the Enigma, trying to comprehend the scale of the implications. This was a secret it was dangerous to know, he thought. This was a secret big enough to swallow a person whole. Ten thousand Poles – our gallant Allies, survivors of an army that had charged the Wehrmacht's Panzers on horseback, waving swords – ten thousand of them trussed, gagged and shot by our other, more recent, gallant Allies, the heroic Soviet Union? No wonder the Registry had been cleared.

An idea occurred to him and he went back to the first cryptogram. For if one looked at it thus:

HYCYKWPIOROKDZENAJEWICZJPTAKJHRUTBPYSJMOTYLPCIE

it was meaningless, but if one rearranged it thus:

HYCYK, W, PIORO, K., DZENAJEWICZ, J.,PTAK, J., HRUT, B., PYS, J., MOTYL, P-

then out of the chaos was conjured order. Names.

He had enough now. He could have stopped. But he went on anyway, for he was never a man to leave a mystery partially solved, a mathematical proof only half worked-out. One had to sketch in the route to the answer, even if one had guessed at the destination long before the journey's end.

Enigma settings for German Army key Vulture, 2 March 1943:

III IV II INK JP DY QS HL AE NW CU IK FX BR

An Ostubaf Dorfmann. Ostubaffoi Obersturmbann-fiihrer. A Gestapo rank.;

TO OBERSTURMBANNFUHRER DORFMANN RHSA ON ORDERS OFFICE COMMANDER IN CHIEF NAMES OF POLISH OFFICERS IDENTIFIED TO DATE IN KATYN FOREST AS FOLLOWS

He didn't bother to write them down. He knew what he was looking for and he found it after an hour, buried in a babble of other names. It wasn't sent to the Gestapo on the 2nd, but on the 3rd:

PUKOWSKI, T.

6

A few minutes after 5 a.m., Tom Jericho surfaced, molelike, from his subterranean hole, and stood in the passage of the mansion, listening. The Enigma had been returned to its shelf, the safe locked, the door to the Black Museum locked as well. The cryptograms and the settings were in his pocket. He had left no trace. He could hear footsteps and male voices coming towards him and he drew back against the wall, but whoever they were they didn't come his way. The wooden staircase creaked as they passed on, out of sight, up to the offices in the bedrooms.

He moved cautiously, keeping close to the wall. If Wigram had gone looking for him in the hut at midnight and failed to find him, what would he have done? He would have gone to Albion Street. And seeing Jericho hadn't turned up there, he might by now have roused a considerable search party. And Jericho didn't want to be found, not yet. There were too many questions he had to ask, and only one man had the answers.

He passed the foot of the staircase and opened the double doors that led to the lobby.

You became her lover, didn't you, Puck? The next after me in the great revolving door of Claire Romilly's men. And somehow – how? – you knew that something terrible was going on in that ghastly forest. Wasn't that why you sought her out? Because she had access to information you couldn't get to? And she must have agreed to help, must have started copying out anything that looked of interest. ('She'd really been much more attentive of late…') And then there came the nightmare day when you realised – who? your father? your brother? – was buried in that hideous place. And then, the next day, all she could bring you was cryptograms, because the British – the British: your trusty Allies, your loyal protectors, to whom the Poles had entrusted the secret of Enigma – the British had decided that in the higher interest they simply didn't want to know any more.

Puck, Puck, what have you done?

What have you done with her?

There was a sentry in the Gothic entry hall, a couple of cryptanalysts talking quietly on a bench, a WAAF with a stack of box files struggling to find the doorhandle with her elbow. Jericho opened it for her and she smiled her thanks and made a rolling motion with her eyes, as if to say: What a place to find ourselves at five o'clock on a spring morning, and Jericho smiled and nodded back, a fellow sufferer: Yes, indeed, what a place.

The WAAF went one way and he went the other, towards the morning star and the main gate. The sky was black, the telephone box almost invisible in the shadows of the arboretum. It was empty. He walked straight past it and pushed his way into the vegetation. Sir Herbert Leon, the last Victorian master of the Park, had been a dedicated arborist, planting his realm with three hundred different species of tree. Forty years of re-seeding, followed by four years without pruning, had turned the arboretum into a labyrinth of secret chambers, and here Jericho squatted on the dry earth and waited for Hester Wallace.

By five fifteen it was clear to him she wasn't coming, which suggested she had been detained. In which case, they were almost certainly looking for him.

He had to get out of the Park, and he couldn't risk the main gate.

At five twenty, when his eyes were thoroughly used to the dark, he began to move northwards through the arboretum, back towards the house, his bundle of secrets heavy in his pocket. He could still feel the effects of the Benzedrine – a lightness in his muscles, an acuteness in his mind, especially to danger – and he offered a prayer of thanks to Logie for making him take it, because otherwise by now he'd be half-dead.

Puck, Puck, what have you done?

What have you done with her?

He came out cautiously from between two sycamores and stepped on to the lawn at the side of the mansion. Ahead of him was the long, low outline of the old Hut 4, with the mass of the big house behind it. He skirted it and went around the back, past some rubbish bins and into the courtyard. Here were the stables where he'd started work in 1939, and beyond those the cottage where Dilly Knox had first pried into the mysteries of the Enigma. Drawn up in a semicircle on the cobbles he could just make out the gleaming cylinders and exhausts of half a dozen motorcycles. A door opened and in the brief glow he saw a dispatch rider, padded, helmeted and gauntleted, like a medieval knight. Jericho pressed himself against the brickwork and waited while the motorcyclist adjusted his pillion, then kicked the machine into life and revved it. Its red light dwindled and disappeared through the rear gate.

He considered, briefly, trying to get out using the same exit, but reason told him that if the main entrance was probably being watched, then so was this. He stumbled on past the cottage, past the back of the tennis courts, and finally past the bombe hut, throbbing like an engine shed in the darkness.

By now a faint blue stain had begun to seep up from the rim of the sky. Night – his friend and ally, his only cover – was preparing to desert him. Ahead, he could begin to make out the contours of a building site. Pyramids of earth and sand. Squat rectangles of bricks and sweet-smelling timber.

Jericho had never before paid much notice to Bletchley's perimeter fence, which turned out, on inspection, to be a formidable stockade of seven-foot-high iron stakes, tapering at their tips into triple spears, bent outwards to deter incursion. It was as he was running his hands over the galvanised metal that he heard a swish of movement in the undergrowth just beyond it, to his left. He took a few steps backwards and retreated behind a stack of steel girders. A moment later, a sentry ambled past, in no great state of alertness, to judge by his slouched silhouette and the shuffle of his step.

Jericho crouched lower, listening as the sounds faded. The perimeter was perhaps a mile long. Say, fifteen minutes for a sentry to complete a circuit. Say, two sentries patrolling. Possibly three.

If there were three, he had five minutes.

He looked around to see what he could see.

A two-hundred-gallon drum proved too heavy for him to shift, but there were planks, and some thick sections of concrete drainage pipe, both of which he found he was able to drag over to the fence. He started to sweat again. Whatever they were building here, it was going to be vast – vast and bombproof. In the gloom the excavations were fathomless. 'FIVE LAYERS CORPSES. UPPER MUMMIFIED LOWER LIQUID…'

He upended the pipes and stood them about five feet apart. He laid a plank on top. Then he hefted a second set of pipes on to the first, picked up another length of timber and staggered over with it balanced on his shoulder. He set it down carefully, making a platform with two steps – about the first practical thing he had made since boyhood. He climbed on to the rickety structure and seized the iron spears. His feet scrabbled for a purchase on the rails. But the fence was designed to keep people out, not in. Fuelled by chemicals and desperation, Jericho was just able to pull himself astride it, twist, and lower himself down the other side. He dropped the last three feet and stayed there, squatting in the long grass, recovering his breath, listening.

His final act was to put his foot through the railings and kick away the planks.

He didn't wait to see if the noise had attracted attention. He set off across the field, walking at first, then trotting and finally running, sliding and skidding over the dewy grass. There was a big military camp to his right, concealed by a line of trees only just now materialising. Behind him, he could sense the dawn on his shoulders, brightening by the minute. He looked back only when he reached the road, and that was his last impression of Bletchley Park: a thin line of low, black buildings – mere dots and dashes along the horizon – and above them in the eastern sky an immense arc of cold blue light.

He had been to Puck's digs once before, on a Sunday afternoon a year ago, for a game of chess. He had a vague memory of an elderly landlady who doted on Puck pouring them tea in a cramped front room, while her invalid husband wheezed and coughed and retched upstairs. He could remember the game quite clearly, it had a curious shape to it – Jericho very strong in the opening, Puck in the middle, and Jericho again at the end. A draw agreed.

Alma Terrace. That was it. Alma Terrace. Number nine.

He was moving quickly – long strides and an occasional, loping run – keeping to the side of the pavement, down the hill and into the sleeping town. Outside the pub lingered a soapy smell of last night's beer. The Methodist chapel a few doors down was dark and bolted, its blistered sign unchanged since the outbreak of war: 'Repent ye: for the Kingdom of Heaven is at hand.' He went under the railway bridge. On the opposite side of the road was Albion Street, and a little further along the Bletchley Working Men's Club ('The Co-Operative Society Presents a Talk by Councillor A. E. Braithwaite: The Soviet Economy, Its Lessons for Us'). After another twenty yards he turned left into Alma Terrace.

It was a street like so many others: a double row of tiny red-brick houses running parallel with the railway. Number nine was a clone of all the rest: two little windows upstairs and one downstairs, all three swathed in blackout curtains as though in mourning, a spade's length of front yard with a dustbin in it, and a wooden gate to the road. The gate was broken, the timber splintered grey and smooth like driftwood, and Jericho had to hoist it open. He tried the door – locked – and hammered on it with his fist.

A loud coughing – as loud and immediate as a woken guard dog. He stepped back a pace and after a couple of seconds one of the upstairs curtains flickered open. He shouted: 'Puck, I need to talk to you.' t

A steady clop-clop of hooves. He glanced up the road to see a coal dray turning into the street. It passed by slowly and the driver took a good, long look at him, then flicked the reins and the big horse responded, the tempo of its hooves increasing. Behind him Jericho heard a bolt being worked and drawn back. The door opened a crack. An old woman peered out.

'I'm so sorry,' said Jericho, 'but it's an emergency, I need to speak to Mr Pukowski.'

She hesitated, then let him in. She was less than five feet tall, a wraith, with a pale blue, quilted housecoat clutched across her nightdress. She spoke with her hand held in front of her mouth and he realised she was embarrassed because she didn't have her teeth in.

'He's in his room.'

'Could you show me?'

She shuffled down the passage and he followed. The coughing from upstairs had intensified. It seemed to shake the ceiling, to swing the grimy lampshade.?

'Mr Puck?' She tapped on the door. 'Mr Puck?' She said to Jericho: 'He must be still asleep. I heard him come in late.'

'Let me. May I?'

The little room was empty. Jericho was across it in three strides, pulling back the curtains. Grey light lit the kingdom of the exile: a single bed, a washstand, a wardrobe, a wooden chair, a small mirror of thick, pink, crystalled glass with birds carved into it, suspended above the mantelpiece by a metal chain. The bed had been lain on rather than slept in, and a saucer by the bedhead was filled with cigarette stubs.

He turned back to the window. The inevitable vegetable patch and hooped bomb shelter. A wall,

'What's over there?'

'But the door was bolted-'

'On the other side of the wall? What's over there?'

With her hand in front of her mouth she looked aghast. 'The station.'

He tried the window. It was jammed shut.

'Is there a back door?'

She led him through a kitchen that couldn't have altered much since Victorian days. A mangle. A hand pump for raising water to the sink…

The back door was unlocked.

'He's all right, isn't he?' She'd stopped worrying about her teeth. Her mouth was trembling, the skin around it furrowed, sunken, brown.

'I'm sure. You go back to your husband.'

He was following Puck's trail now. Footprints – large footprints – led across the vegetable patch. A tea chest stood against the wall. It bowed and splintered as Jericho mounted it, but he was just able to fold himself over the top of the sooty brickwork. For a moment he almost tumbled head first on to the concrete path, but then he managed to brace himself and brought his legs up.

In the distance: the whistle of a train.

He hadn't run like this for fifteen years, not since he was a schoolboy being screamed at on a five-mile steeplechase. But here they were again, as grim as ever, the familiar instruments of torture – the knife in his side, the acid in his lungs, the taste of rust in his mouth.

He tore through the back entrance into Bletchley Station and flailed around the corner on to the platform, through a cloud of leaden-coloured pigeons that flapped and rose heavily and settled again. His feet rang on the ironwork of the footbridge. He took the stairs two at a time and ran across the gantry. A fountain of white smoke spurted up to his left, his right, and filtered through the floorboards, as the locomotive passed slowly underneath.

The hour was early, the waiting crowd was small, and Jericho was halfway down the steps to the northbound platform when he spotted Puck about fifty yards away, standing close to the tracks, holding a small suitcase, his head turning to follow the slow parade of compartments. Jericho stopped and clutched the hand rail, bent forwards, struggling for air. The Benzedrine, he realised, was wearing off. When the train at last jolted to a stop, Puck looked around, walked casually towards the front, opened a door and disappeared.

Using the rail to support himself, Jericho picked his way down the last few steps and almost toppled into an empty compartment.

He must have blacked out, and for several minutes, because he never heard the door slam behind him or the whistle blow. The next thing he was conscious of was a rocking motion. The banquette was warm and dusty to his cheek and through it he could feel the soothing rhythm of the wheels – dah-dah-dee-dee, dee-dee-dah-dah, dah-dah-dee-dee… He opened his eyes. Smudges of bluish cloud edged in pink slipped slowly across a square of white sky. It was all very beautiful, like a nursery, and he could have fallen asleep again, but for a vague recollection that there was something dark and threatening he was supposed to be afraid of, and then he remembered.

Levering himself up, he ministered to his aching head – shook it, rotated it in a figure of eight, then pushed down the window and thrust it into the cold draught of rushing air. No sign of any town. Just flat, hedged countryside, interspersed with barns and ponds that glinted in the morning light. The track was curving slightly and ahead he could see the locomotive flying its long pennant of smoke above a black wall of carriages. They were heading north on the main west-coast line, which meant – he tried to recall -Northampton next, then Coventry, Birmingham, Manchester (probably), Liverpool…

Liverpool?

Liverpool. And the ferry across the Irish Sea.

Jesus.

He was stunned by the unreality of it all, yet at the same time by its simplicity, its obviousness. There was a communication cord above the opposite row of seats ('Penalty for improper use:?20') and his immediate reaction was to pull it. But then what? Think. He would be left, unshaven, ticketless, drug-eyed, trying to convince some sceptical guard there was a traitor on board, while Puck – what would Puck do? He would climb down from the train and disappear. Jericho suddenly saw the full absurdity of his own situation. He didn't even have enough money to buy a ticket. All he had was a pocketful of cryptograms.

Get rid of them.

He pulled them from his pocket and tore them into fragments, then hung his head back out of the window and released them into the slipstream. They were whipped away, borne up and over the top of the carriage and out of sight. Craning his head the other way, he tried to guess how far up the train Puck was. The force of the wind stifled him. Three carriages? Four? He pulled back in and closed the window, then crossed the swaying compartment and slid open the door to the corridor.

He peered out, carefully.

The rolling stock was standard, pre-war, dark and filthy. The corridor, lit for the blackout by faint blue bulbs, was the colour of a poison bottle. Four compartments off to one side. A connecting door at the front and rear led into the adjacent carriages.

Jericho lurched towards the head of the train. He glanced into each compartment as he passed. Here were a pair of sailors playing cards, there a young couple asleep in one another's arms, there again a family – mother, father, boy and girl – sharing

sandwiches and a flask of tea. The mother had a baby at her breast and turned away, embarrassed, when she saw him looking.

He opened the door leading to the next carriage and stepped into no man's land. The floor shifted and pitched beneath his feet like a catwalk at a funfair. He stumbled and banged his knee. Through a three-inch gap he could see the couplings clanking and, beneath them, the rushing ground. He let himself into the other carriage in time to see the big, unsmiling face of the guard emerging from a compartment. Jericho slipped smartly into the lavatory and locked himself in. For a moment he thought he was sharing it with some tramp or derelict but then he realised that this was him – the yellowish face, the dwindled and feverish eyes, the windblown hair, the two days' growth of blue-black beard – this was his reflection. The toilet was blocked and stinking. A trail of sodden, soiled paper curled from its bowl and wrapped around his feet like an unravelled bandage.

'Ticket please.' The guard rapped loudly. 'Slide your ticket under the door, please.'

'It's in my compartment.'

'Oh, is it then?' The handle rattled. 'You'd better come and show me.'

'I'm not feeling awfully well.' (Which was true.) I've left it out for you.' He pressed his burning forehead the cool mirror. 'Just give me five minutes.'

The guard grunted. 'I'll be back.' Jericho heard of rush of wheels as the connecting door opened, then the slam of it closing. He waited a few seconds then flipped open the lock.

There was no sign of Puck in this carriage, or in the next, and by the time he'd leaped the gyrating iron plates into the third he could sense the train beginning to slow. He moved on down the corridor.

Two compartments filled with soldiers, six in each sullen-looking, their rifles stacked at their feet.

Then one empty compartment.

Then Puck.

He was sitting with his back to the engine, leanin forwards – the same old Puck, handsome, intense, his elbows on his knees, engrossed in conversation with someone just out of Jericho's line of sight.

It was Claire, thought Jericho. It had to be Claire. It would be Claire. He was taking her with him.

He turned his back on the compartment and moved discreetly crabwise, pretending to look out of the dirty window. His eyes registered an approaching town -scrubland, goods wagons, warehouses – and then an anonymous platform with a clock frozen at ten to twelve, and faded posters with jolly, buxom girls advertising long-dead holidays in Bournemouth and Clacton-on-Sea.

The train crawled along for a few more yards, then stopped abruptly opposite the station buffet.

'Northampton!' shouted a man's voice. 'Northampton Station!'

And if it was Claire, what would he do?

But it wasn't her. He looked and saw a man, a young man – neat, dark, tanned, aquiline: in every essence, foreign – saw him only briefly because the man was already up on his feet and releasing Puck's hand from a double clasp. The young man smiled (he had very white teeth) and nodded – some transaction had been completed – and then he was stepping out of the compartment and was moving quickly across the platform, sharp shoulders slicing through the crowd. Puck watched him for a moment, then pulled the door shut and sank back into his seat, out of sight.

Whatever his escape plans, they did not appear to include Claire Romilly.

Jericho jerked his gaze away.

Suddenly he saw what must have happened. Puck cycling over to the cottage on Saturday night to retrieve the cryptograms – and instead finding Jericho. Puck returning later to discover the cryptograms were missing. And Puck assuming, naturally, that Jericho had them and was about to do what any loyal servant of the state would do: run straight to the authorities and turn Claire in.

He glanced back at the compartment. Puck must have lit a cigarette. Films of smoke were settling into wide, steel-blue strata.

But you couldn't allow that, could you, because she was the only link between you and the stolen papers? And you needed time to plan this escape with your foreign friend.

So what have you done with her?

A whistle. A frantic working-up of steam. The platform shuddered and began to slide away. Jericho barely noticed, unconscious of everything except the inescapable sum of his calculations.

What happened next happened very quickly and if there was never to be a single, coherent explanation of events, that was due to a combination of factors: the amnesia induced by violence, the deaths of two of the participants, the bureaucratic fog-machine of the Official Secrets Act.

But it went something like this.

About two miles north of Northampton Station, close to the village of Kingsthorpe, a set of points connected the west-coast main line with the branch line to Rugby. With five minutes' notice, the train was diverted off its scheduled course, westwards down the branch line, and very shortly afterwards a red signal warned the driver of an obstruction on the tracks ahead.

The train was therefore already slowing, although he didn't recognise it, when Jericho slid open the door to Puck's compartment. It moved very easily, at a finger's pressure. The layers of smoke rippled and erupted.

Puck was just extinguishing the cigarette (his ashtray was subsequently found to contain five stubs) and he was pushing down the window – presumably because he had noticed the loss of speed, and maybe the diversion, and was suspicious and wanted to see what was happening. He heard the door behind him and turned, and his face, in that instant, became a skull. His flesh was shrunken, tautened, masklike. He was already a dead man, and he knew it. Only his eyes were still alive, glittering beneath his high forehead. They flickered from Jericho to the corridor to the window and back to Jericho. A frantic effort was going on behind them, you could see, a mad and hopeless attempt to compute odds, angles, trajectories.

Jericho said: 'What have you done with her?'

Puck had the stolen Smith and Wesson in his hand, safety catch off. He brought it up. His eyes went through the same routine: Jericho, corridor, window, then Jericho again and finally the window. He tilted his head back, keeping the gun held out at arm's length, and tried to see up the track.

'Why are we stopping?'

'What have you done with her?'

Puck waved him back with the gun, but Jericho didn't care what happened now. He took a step closer.

Puck began to say something like 'Please don't make me' and then – farce, as the door slid open and the guard came in for Jericho's ticket.

For a long moment they stood there, this curious trio – the guard with his large, bland face, creasing with surprise; the traitor with his wavering pistol; the cryptanalyst between them – and then several things happened more or less at once. The guard said 'Give me that' and made a lunge at Puck. The gun went off. The noise of it was like a physical blow. The guard said 'Ooof?' in a puzzled way, and looked down at his stomach as if he had a bad twinge of indigestion. The wheels of the train locked and screamed and suddenly they were all on the floor together.

It may have been that Jericho was the first to crawl free. Certainly he had a memory of actually helping Puck to his feet, of pulling him out from beneath the guard, who was making a ghastly keening sound and leaking blood everywhere – from his mouth and his nose, from the front of his tunic, even from the bottom of his trouser legs.

Jericho knelt over him and said, rather fatuously, because he'd never seen anyone injured before: 'He needs a doctor.' There was a commotion in the corridor. He turned to find that Puck had the outside door open and the Smith and Wesson pointed at him. He was clasping the wrist of his gun hand and wincing as if he'd sprained it. Jericho closed his eyes for the bullet and Puck said – and this Jericho was sure of, because he spoke the words very deliberately, in his precise English: 'I killed her, Thomas. I am so terribly sorry.'

Then he vanished.

The time by now was just after a quarter past seven – 7.17, according to the official report – and the day was coming up nicely. Jericho stood on the threshold of the carriage and he could hear blackbirds singing in the nearby copse, and a skylark above the field. All along the train, doors were banging open in the sunshine and people were jumping out. The locomotive was leaking steam and beyond it a group of soldiers were scrambling down the slight embankment, led – Jericho was surprised to see – by Wigram. More soldiers were deploying from the train itself, to Jericho's right. Puck was only about twenty yards away. Jericho jumped down to the grey stones of the track and set off after him.

Someone shouted, very loudly, almost directly behind him: 'Get out of the fucking way, you fucking idiot!' – wise advice, which Jericho ignored.

It couldn't end here, he thought, not with so much still to know.

He was all in. His legs were heavy. But Puck wasn't making much progress either. He was hobbling across a meadow, trailing a left ankle which autopsy analysis would later show had a hairline fracture – whether from his fall in the compartment or his leap from the train, no one would ever know, but every step must have been agony for him. A small herd of Jersey cattle watched him, chewing, like spectators at a running track.

The grass smelled sweet, the hedges were in bud, and Jericho was very close to him when Puck turned and fired his pistol. He couldn't have been aiming at Jericho – the shot went wide of anything. It was just a parting gesture. His eyes were dead now. Sightless,

blank. There was an answering crackle from the train. Bees buzzed past them in the spring morning.

Five bullets hit Puck and two hit Jericho. Again, the order is obscure. Jericho felt as though he had been struck from behind by a car – not painfully, but terrifically hard. It winded him and pitched him forward. He somehow kept on going, his legs cartwheeling, and saw tufts flying out of Puck's back, one, two, three, and then Puck's head exploded in a red blur, just as a second blow – irresistible this time – spun Jericho from his right shoulder round in a graceful arc. The sky was wet with spray and his final thought was what a pity it was, what a pity it was, what a pity it was that rain should spoil so fine a morning.