Yukawa often likened police investigations to scientific experiments, but this time the comparison felt particularly compelling.
“I see. I’ll relay your explanation to the chief — though I doubt I’ll be as eloquent as you, Professor.”
“Give it your best shot.”
“I have one more question. Why did you think that Masumura might have some kind of link to that murder case from twenty-three years ago?”
“That’s easy enough to answer. Masumura had to be involved in Hasunuma’s murder for my hypothesis to hold up. I’m referring to my hypothesis about the killer transforming the little room into a gas chamber for an execution. A number of conditions had to be in place for the hypothesis to work. Let me tell you about three of them.”
“Just a moment.” Kaoru pulled a notebook from her bag and readied herself to take notes. “Go on, please.”
Yukawa took a sip of coffee, then raised an index finger.
“First, the killer had to get Hasunuma to take some sleeping medication. Second, Hasunuma had to fall asleep specifically inside the little storeroom. Third, the killer had to be aware that the little room could be locked from the outside. Those are my three conditions.”
Yukawa had rattled them off and Utsumi was having trouble keeping up. “Okay. And?”
“Masumura was the only person who fulfilled all three conditions. It was easy for him to get Hasunuma to drop his guard and to slip sleeping medication into his drink. Since they lived together, Masumura obviously knew where Hasunuma slept. The most crucial condition is number three. Unless you actually lived in the hut, you would never know that the sliding door could be locked shut.”
Utsumi raised her eyes from the scrawl in her notebook and looked thoughtfully at the physicist.
“It seems so obvious when you explain it.”
“You think I’m right?”
“So obvious, I’m almost disappointed.”
Yukawa frowned. “I disappointed you?”
“No, I disappointed myself. I mean, why couldn’t I figure out something so simple? The chief will be annoyed with himself, too.”
“It’s because both of you had made up your minds that Masumura had no connection to the case. Hasunuma went to live in Masumura’s place of his own volition; the two men met long before the death of Saori Namiki; and, to top it all, Masumura had an alibi. He was one of the first people to be struck from the suspect list.”
“But that’s not how you looked at it, Professor.”
“No. Kusanagi told me that there was no point of contact between Masumura and the Namiki family. In that case, Masumura’s motive had to predate Saori’s death. Could something have happened when the two men were working at the recycling firm where Masumura is still employed? Hardly. If there had been friction between them, Hasunuma would not have gone to live in Masumura’s spare room later, would he? That was when I tried flipping the problem.” Yukawa turned his hand palm upward to illustrate his point. “The question became had Masumura met Hasunuma completely randomly, or did Masumura actively seek him out? Once Masumura managed to track him down, did he insinuate himself into the same workplace, befriend Hasunuma, and wait for an opportunity to take his revenge? Hasunuma, however, quit his job and moved on before Masumura could execute his plan. A few years later, the opportunity to do so presented itself in an unexpected fashion. This time, it was Hasunuma who approached Masumura. And, this time, Masumura was determined to settle his decades-old score. Okay, if we assume that all that was indeed the case, then what was this old grudge of Masumura’s?”
“That’s when you realized that Masumura might have a connection to the Yuna case.”
“Yes, if my hypothesis was correct, he had to.” Yukawa swallowed a mouthful of coffee with an air of smug composure.
“What about Masumura’s alibi?”
“I don’t think he’s lying about that. Masumura is just an accomplice. He didn’t do the deed himself.”
“You think someone else is the principal?”
“I suppose I must.” Yukawa put down his cup with a sigh. “This problem is not a simple one. To be honest with you, my hypothesis remains something of a work in progress. I still haven’t solved the mystery central to the whole thing.”
“What do you mean? Is it something to do with the method that was used?”
“No, I think I’ve got that covered.” Yukawa sounded confident.
“The idea of converting the little room into a gas chamber?”
“Yes.”
“What should we be thinking about the helium issue? You were the one who said that a huge amount of helium would be needed.”
“I’d like to hear the results of that thing, before I go into that. You know, that thing I asked you to get Forensics to check up on? Did they get back to you?”
“They gave me a written report. I’ve brought the results with me.” Utsumi extracted several folded sheets of paper from inside her bag and placed them on the table.
After adjusting his glasses, Yukawa picked up the report.
“How is it?” Kaoru asked somewhat timidly. “The guy in charge at Forensics was actually rather skeptical. ‘Why does Professor Yukawa care about something like that?’”
Yukawa’s mouth, which had been a stern straight line, suddenly creased into a smile. His eyes twinkled.
“This is fantastic,” the physicist said. “Now I think we need Forensics to conduct a little experiment for us. Naturally, I’ll have to be there myself.”
33
The young technician from Forensics was down on one knee in front of the sliding door, using a screwdriver to loosen the screws that kept the door handle in place.
Having removed all the screws, the technician detached the handles from both sides of the door, revealing what Yukawa had referred to as the Judas Window.
Utsumi peered over the technician’s shoulder. “It’s true. It goes right through.”
“That’s absolutely key,” said Yukawa, who was standing next to Kusanagi behind Utsumi. “What can you get through a small square hole of this size is the crucial question.”
“A hole this size is fine,” said Shimaoka, the director of Forensics. He was there to both direct and observe the test.
They were about to conduct an experiment in Eiji Masumura’s small apartment. Kusanagi, Utsumi, and Yukawa were the only non-technicians there. They planned to photograph every stage of the experiment using multiple cameras and report back to Director Mamiya and the other top brass.
The young technician had moved away from the sliding door, so Kusanagi peered into the little room, which was the actual crime scene. Inside, everything was ready.
A ground sheet had been laid over the parquet floor and a mattress and quilt placed on top of it. A mannequin lay on the mattress. It was a crash test dummy but had the same weight, articulation, and size as a real person.
“We’ve tried to re-create the scene exactly as it was when the body was found. The mattress and the quilt are identical,” Shimaoka said. “The victim’s actual bedding is not available, so we’ll be using a brand-new quilt and mattress. Is that all right, Professor Yukawa?”
“You know their weight?”
“Yes, we’ve already weighed them.”
“That’ll be fine then. Thanks very much.”
Kusanagi examined the little room. Cameras had been set up in two locations and several square devices eight inches high were dotted around the room. One of them was very close to the dummy.