A Midsummer's Equation

FIFTY-SIX

“We found no issues with Sawamura’s statement,” Nonogaki said. “The people at the bar confirmed the time of his arrival after he disposed of the body, and the timing fits with the distance between the Green Rock Inn and the place where the body was found. There were, of course, no witnesses to any of this, but given the time and the location, that was to be expected. That’s all I’ve got for now,” he added crisply and took a seat.

The mood in the conference room in the Hari Police Department, where the investigative task force was meeting, was considerably different from what it’d been several days before. In particular, Commissioner Tomita and Chief Okamoto looked relieved that the days they would have to spend with the Shizuoka prefectural police breathing down their necks were numbered.

Among the detectives from prefectural homicide, however, there were a few glum looks. A closed case was a closed case, but the trail that had begun with an abandoned body had led them not to a homicide but to professional negligence resulting in death—a far less satisfying outcome.

Shigehiro and Setsuko Kawahata had both acknowledged the details of Sawamura’s story. They claimed they had lied because they didn’t want to burden one of their daughter’s friends, but now that he’d confessed himself, there was no longer any reason to hide the truth.

Physical evidence in support of their story was piling up, too. An examination of Sawamura’s pickup truck revealed several hairs in the flatbed. Though they were still running DNA tests, from the shape and composition of the hairs, it looked extremely likely that they belonged to Masatsugu Tsukahara.

The sleeping pill that Shigehiro had given to Tsukahara matched ones they found in the drawer of the living room table. They had gotten confirmation from the doctor who gave Shigehiro the pills as well—prescribed five years earlier for mild insomnia.

Yet there were still a few unanswered questions, the most pressing of which being exactly how Tsukahara had died.

The chief forensics officer stood and reported that his team had been up at the Green Rock Inn again that morning attempting to reproduce the conditions on the night of Tsukahara’s death.

“Basically,” he explained, “there were no major malfunctions in the boiler itself. However, we did find that by blocking the air duct leading down to the boiler, we could create a low-oxygen burn. The suspect was not clear on how the air duct might’ve been blocked, but we did find a cardboard box nearby that could’ve done the trick if, say, it had been standing near the vent and fallen over, blocking it. We furthermore went on to check the carbon monoxide concentration in the Ocean Room on the fourth floor in the event of a low-oxygen burn in the boiler. In our tests yesterday we were able to achieve a maximum concentration of one hundred ppm, with an average between fifty and sixty ppm. In addition, we discovered that the boiler was fit with a detection device designed to automatically stop improper burns after thirty minutes. However, a burn of that length is insufficient to produce the level of carboxyhemoglobin found in the body.”

“So what happened? Do we have an explanation for any of this?” Chief of Homicide Hozumi asked, his eyebrows knitting in frustration.

“We think that other conditions may have played a factor.”

“What other conditions?”

“The weather on the night in question, for one. If a strong wind blew, pushing smoke back down the chimney, carbon monoxide levels could rise dramatically. We estimate concentration in the room could have reached as high as a thousand ppm.”

“Okay,” Hozumi said, nodding. “So would it be fair to say that, basically, we’re still looking at negligence as the root cause of the accident, but the fatality was due to a number of coincidental factors?”

“That’s correct. Of course, we’re still running tests.”

“Right, carry on,” Hozumi said, his earlier consternation gone.

Things were drawing to a close, Nishiguchi thought. If the conditions leading to the death were so specific it was impossible for even forensics to re-create them, it made the possibility that Shigehiro had intentionally caused the poisoning extremely slim.

But what Yukawa had said the day before still bothered him. How had he known that forensics wouldn’t be able to re-create the accident? Could it be because the physicist knew how it was done?

Motoyama stood and began giving his own report on news they’d received from Tokyo concerning Hidetoshi Senba. Hozumi was chatting and laughing with Isobe. Most of the other ranking officers weren’t even listening. It was clear that the room had lost interest in Senba and their suspect’s past.

And once the case was closed and a little time had passed—

I’ll go pay Narumi a visit, Nishiguchi thought. The presence of an officer might comfort her. He could be with her the entire time while the trial was going on.

A smile slowly spread across Nishiguchi’s face as the cloud over his thoughts lifted.