It is 2023. Saskia Brandt of the Berlin Förderatives Investigationsbüro (FIB) has just solved the most baffling murder of her career. Over the past twelve hours, she has followed clues that lead only to one conclusion: she is the murderer. Upon this realization, her boss appears to explain that her violent criminal past has been erased from her mind and a chip implanted in her brain. This chip imposes a donor personality, a blank slate on which the FIB can draw any skill or knowledge. “It takes a murderer to catch a murderer,” her boss says, and congratulates her. She is now a full Kommisarin.
Saskia’s first assignment after this revelation is to find Professor David Proctor. In 2003 he was suspected — but never convicted — of bombing a Scottish research institute. Now he has detonated a second bomb in the same location. This bomb has killed a man called Bruce Shimoda, David’s former research partner. Now David is on the run.
Saskia flies to Edinburgh. At the airport, she meets a middle-aged Scottish detective called Jago. They verbally spar with each other and become friends. Saskia learns that David was briefly held in custody following the murder but escaped with the aid of an unidentified woman. Many suspect this woman to be his daughter, Jennifer, who is a world-leading physicist working in a secret research centre in Nevada called Met Four Base, where she presides over Project Déjà Vu. Only days have passed since she successfully sent the first matter through time using Project Déjà Vu’s machine.
The chase is on. Saskia tracks David with a combination of luck, nerve, implanted skill, and gut instinct. Throughout the chase, she must tamp down the flickers of strangely familiar associations and fragments of random memories in a mind that is supposed to be entirely blank and new, designed and controlled only by the FIB. They meet at night at Heathrow after a pursuit across the remote Scottish and British countryside. David manages to reach the aircraft and Saskia boards it as it takes off.
En route, Saskia and David connect. She tells him her story, and makes clear her determination to take her own life should her past mind, that of a murderous criminal, take over. David warms to Saskia but knows that a return to Britain means jail. He threatens to use his electronic companion, a credit-card-sized computer called Ego, to take over Saskia’s brain chip and effectively switch her off. Saskia’s hand is forced. Reluctantly, she helps him escape the American authorities upon landing and they go on the run, destination Nevada and Project Déjà Vu. David doesn’t know why he has to go there, but the same mysterious woman who helped him escape custody after the bombing of the lab has, cryptically, instructed him to do so.
Jennifer surprises both David and Saskia by asking them to follow her into the research centre. Then David reveals what he has known since meeting Saskia on the aeroplane to the US: that the woman who helped him escape from custody in Scotland was Saskia Brandt herself. Saskia is incredulous at first. She cannot believe that there is an older version of herself walking around the world of 2023. It has echoes of her first case as a Kommissarin: the mastermind of the crime under investigation has turned out to be herself.
Their conversation is halted by the appearance of John Hartfield, the co-owner of the research station. He wants to use Project Déjà Vu to travel backwards in time and force his younger self to accept an antidote to the experimental medical treatment that cured his cancer but re-shaped his mind. For Hartfield, the world of 2023 can go to hell. Hartfield escapes by doing the one thing that Saskia fears most: he sends a wireless command that deactivates her brain chip. As Hartfield flees, Saskia feels her conscious self as an FIB agent evaporate and the half-remembered life of Ute, the murderer within Saskia, overwhelm her.
Saskia experiences a waking dream in which she recalls the rape and attempted murder of a woman called Ute Schlesinger by a cabal of sexual predators in Cologne. The woman plans her revenge and takes it, killing them all. Saskia comes to understand that Ute is not a woman to be feared; she is a survivor. That instinct that Saskia has always felt inside her was not criminal intent. It was courage.
She understands that the only way to stop Hartfield is to surrender herself to the identity of Saskia Brandt once more. Again the courage. When she opens her eyes, it is Saskia who looks out. Hartfield has beaten them to the time machine, however, and left for 2003. Saskia understands that she will need to follow him back in time. In one sense, it is an escape from her indentured employment with the FIB. In another sense, it is a trap: she will become her future self, the woman who helped David escape. Just like her recruitment into the FIB, it is a choice without choice.
David and Jennifer help Saskia return to the research centre in rural Scotland in the autumn of 2003, the day it was first bombed. Saskia is half an hour ahead of Hartfield. But at the time he is due to arrive, there is an underground explosion. The only explanation can be that the time machine changed Hartfield’s destination and time and used his mass to trigger a detonation. Who changed the time machine’s settings? Again, it is the person that Saskia has been pursuing all along: her future self. Saskia escapes from the burning research centre uninjured and slips away from the authorities to start a new life in 2003, free of the FIB but not free of her destiny, and still with questions about herself. If her body is Ute Schlesinger, who is her mind? And who can she trust to help her if she needs it? In her pocket, she discovers a list of major upcoming sports events and their outcomes written by David Proctor. She smiles at this small human connection and then walks into anonymity.