Cold air came wafting toward them. They gasped and shivered.
“Oh, it’s chilly — no, more like downright cold,” Utsumi said.
“No surprise there. Twenty liters of liquid nitrogen at a temperature of minus one hundred and ninety-six degrees has just vaporized,” Yukawa said. “Quite a long time ago, this really heartbreaking accident took place in a research facility up in Hokkaido. The temperature in the low-temperature testing room started rising because the temperature-control machinery had broken down. The staff poured large quantities of liquid nitrogen onto the floor in an effort to get the temperature back down as fast as they could. They must have panicked, as they completely forgot to ventilate the room properly. In the end, they were all asphyxiated.”
“I hadn’t heard about that,” Kusanagi said.
“Something similar must have happened when Masumura opened the sliding door after getting back from wherever he had been. Since he was aware of the dangers of liquid nitrogen, I suppose he didn’t go directly inside.”
The technician at the computer said, “Oxygen concentration is now above twenty percent.”
Shimaoka nodded to Yukawa. “Go ahead, Professor.”
Yukawa went inside. Kusanagi followed him.
The interior of the room didn’t appear to have changed. The white mist had already dispersed.
Yukawa, who was looking down at the floor near his feet, stopped and extracted a pair of leather gloves from his pocket. He pulled them on, squatted down, and picked something up off the floor.
“What have you got there?” Kusanagi asked.
Yukawa opened the palm of his gloved hand to reveal something that looked like a small, thin rice cracker.
“The liquid nitrogen was all pumped into a single spot in the room. That area was supercooled in a very extreme fashion. The carbon dioxide in the air got frozen as well as the water vapor. This here is dry ice.”
“Forensics didn’t report finding any.”
“Of course they didn’t. Masumura would have got rid of it.”
“Oh, right...”
Still clutching the little piece of dry ice, Yukawa started touching the walls, before crouching down to scrutinize the ground sheet.
“What is it?” Kusanagi asked. “Have you noticed something else?”
Yukawa pulled himself to his feet and adjusted his spectacles on his nose.
“I know that I’m repeating myself, but the key thing is what happens to the water vapor in the atmosphere. It will vary depending on the conditions — the temperature, the humidity, the degree of airtightness, and so on — but I thought it possible we might find some waterdrops on the ground sheet. As far as I can see, though, there aren’t any. There is a certain amount of moisture on the walls, but nothing one could describe as abnormal. Anyway, the walls would have dried somewhat, or possibly even reverted to their original state by the time the crime scene was inspected. What do you think, Director?”
Shimaoka and his crew of technicians were busy rolling up the mattress and quilt and tying them with string in preparation for attaching them to a suspension weighing scale.
“The pre-experiment weight of mattress and quilt was thirteen point eight pounds. According to the digital readout here, that’s now increased to fourteen point one pounds. A weight gain of roughly three and a half ounces.”
“Which is the equivalent of half a cup’s worth of water. That tallies perfectly with the condition of the mattress and quilt found at the scene,” said Yukawa. He turned to Kusanagi. “We seem to be one step closer toward proving my hypothesis.”
34
A search and seizure warrant was issued for Tojima-ya Foods, the company owned and managed by Shusaku Tojima, the day after they ran the liquid nitrogen experiment. Kusanagi, who took personal charge of the search, went to the managing director’s office with Detective Sergeant Utsumi and Detective Inspector Kishitani.
Tojima recoiled at the sight of the warrant. “What is the meaning of this?” he protested. “Are you trying to say that my company’s got something to do with your murder investigation? We’re just a food-processing company! We’re not doing anything illegal here!”
“In that case, you’ve got nothing to worry about. Kindly cooperate with the search,” Kusanagi said, returning the warrant to his chest pocket.
It was something that Yukawa had said to him after the liquid nitrogen experiment that inspired him to order the search.
“When I realized that liquid nitrogen had probably been used and not helium,” the professor had told him, “I realized something else, something important: Someone very close to the Namiki family could get his hands on liquid nitrogen with ease. Shusaku Tojima, the childhood friend of Yutaro Namiki, runs his family company, which handles frozen food. You can use a whole range of machines to freeze food, but flash-freezing systems rely on liquid nitrogen.”
Yukawa went on to explain that he’d already spoken to Tojima in order to confirm his hunch.
“It was after Detective Utsumi came to visit me at the university research center. I went to Namiki-ya specifically at a time I knew Tojima would be there, too. I managed to share a table with him, so I got the chance to ask him what freezer systems he used. As I’d expected, Tojima-ya Foods did use liquid-nitrogen-based freezer systems. Chiefly for desserts, he said. I questioned Tojima pretty persistently, so I may have aroused his suspicions.”
This was important. Kusanagi had no excuse for dillydallying. He quickly pushed through the necessary paperwork to execute a search of Tojima’s company premises.
Some eight hours after the search of Tojima-ya Foods had ended, Kusanagi was in the meeting room at the Kikuno precinct station with Utsumi and Kishitani, giving an update to Director Mamiya.
“From interviews we have conducted, we have learned that this March there was an accident involving liquid nitrogen at Tojima-ya Foods,” said Kusanagi, referring to his notes. “Instead of using an automatic freezer, one of the workers was manually spraying some food products with liquid nitrogen, when he lost consciousness and collapsed. The cause of the accident was poor ventilation. The worker’s condition wasn’t life-threatening or even especially serious, but further missteps could have resulted in death.”
“And you think that the accident gave Tojima the idea for the murder?” Mamiya asked.
“We don’t know whether it was Tojima himself who had the idea or someone he mentioned the accident to,” Kusanagi replied circumspectly. “Detective Utsumi!” His tone was suddenly peremptory.
Utsumi tapped a few strokes on the keyboard, then swiveled her laptop around so that it faced Mamiya. On this display was the entrance of the Tojima-ya Foods factory.
“This footage comes from the security camera at the entrance to the Tojima-ya Foods factory. It’s from the day of the parade and, as you can see from the time stamp, it’s from around one o’clock. As it’s a Sunday, you’d expect the whole place to be closed, but the shutter on the loading dock is up.”
Utsumi tapped her keyboard and the video started to play. A minivan drove up to the loading dock. Mamiya gasped.
“I’m now going to jump a few minutes forward.” She fast-forwarded the video to 1:20. The minivan was driving away from the loading dock.
“Can we see the driver’s face?” he asked.
“With this particular footage, we can’t. But there is some from another camera.” Kusanagi shot a glance at Utsumi.
Utsumi pulled up another video. It showed a line of minivans parked in a row.
“This is the parking lot for commercial vehicles at Tojima-ya Foods,” Utsumi explained. “The time’s slightly earlier than the other video. See. The time stamp is 12:56.”