Pathway to Japanese Literature

The Doctor's Death

It was a cold, cold morning on January 17th.
Four or five days ago, after an unprecedented heavy snow had fallen, the skies had remained overcast every day since, and today as well, white flakes were fluttering down.

Tsukahara Toshio and I, having finished breakfast, were in the office-cum-laboratory sitting around the fireplace discussing various matters.
Then around ten o'clock came a knock at the front door. When I opened it stood a beautiful young lady of about twenty years with swollen eyelids and an air of worry about her.

"Is Mr. Tsukahara Toshio present?"

The young lady handed me a small business card.

"Please tell him you've come with a request."

Toshio looked at the business card I had handed him,

"Please come in."

he said.
The business card read "Endō Yukiko."

Before long, the young lady sat down facing Toshio across the table.

“You may already be aware, but I am Endō Shin’ichi’s daughter.”

“Ah, so you’re Dr. Endō’s daughter? Is the professor still engrossed in his research?”

Toshio said.

The young lady suddenly made a sorrowful face,

“The truth is, my father passed away last night.”

“Excuse me?”

Toshio jumped up in surprise.

“Is that true?”

“Yes… and that he was killed by someone.”

Toshio grew even more astonished.
Dr. Endō referred to here was Endō Kōgaku Hakushi, a professor at Tokyo Imperial University. The poison gas discovered by Dr. Endō was far more potent than any previously known, and its manufacturing method had been classified as a state secret—so much so that it was even rumored spies from Western nations had infiltrated to steal this secret.

However, whether the slip of paper detailing its manufacturing method was hidden in his university office or kept at home—no one but Dr. Endō himself had known. Having just heard from the doctor’s daughter about his suspicious death, I thought that Dr. Endō might have been killed by spies trying to steal the secret of his poison gas. Toshio had apparently thought the same thing,

“So it was the work of those notorious spies after all?”

he asked.

“No, it’s that my brother was taken by the police as the suspect.”
“However, my brother is absolutely not the kind of person who would kill my father.”
“That is why I have come to request Mr. Toshio’s assistance in investigating this case.”

“Please explain the circumstances in detail.”

According to the young lady’s account, Dr. Endō had been short-tempered by nature, but after his wife passed away five years prior, he had become even more irritable. The son, Mr. Nobukiyo, was a twenty-four-year-old young man this year; however, his personality was completely different from that of his father, the Doctor—he was fond of literature, and on every matter, his opinions clashed with the Doctor’s. For the past three years, having even suffered harm to his health, he had been staying at a certain inn in Suma for convalescence, living by writing novels and such, and during that time had not returned home even once.

However, six days ago now—that is, on the evening of January 11th—when the Doctor returned from a certain gathering, he had contracted influenza and developed a fever, it was said.
The Doctor disliked seeing physicians and always took medicine based on his own diagnosis, it was said.
It was decided he would retire from the university this April, and though he had grown quite withdrawn of late—perhaps made suddenly lonely by his illness—on the 12th it was said he asked to have Nobukiyo summoned by telegram, stating there were matters he wished to discuss.

Thereupon, the young lady sent telegrams to her brother both on that day and the 13th—twice in total—but from her brother came a reply stating he had no desire to return, it was said. Thereupon, Dr. Endō told the young lady to go to Suma and bring him back, so she entrusted the house to Saitō, the live-in student, and the old servant, departed on the night of the 13th, spent two full days persuading her brother, left Suma early yesterday morning with him, and returned home around 1 AM last night, it was said.

“However, when we returned last night, Father was inexplicably furious and wouldn’t let us into the sickroom.”
“Mr. Saito came out and suggested it would be better to meet him tomorrow morning when his mood improved, so my brother and I slept in separate rooms.”
“Exhausted from the journey, I slept soundly and knew nothing until this morning when the old servant came to inform me of Father’s murder.”

The young lady paused there, gazed at Toshio’s face, then continued her account.

“When I inquired about the circumstances—it seems Father asked Mr. Saitō around one o’clock last night—Mr. Saitō having nursed him until then—to wake Brother and bring him over. When Brother went there, Father was lying in a dimly lit room with his face buried in the futon, but after sending Mr. Saito to bed and when they were alone, he reportedly used harsh words toward Brother without even properly looking at his face. It seems Brother argued back against this but after about ten minutes left without having made any progress and returned again to his own living room to sleep. However, this morning Father was found strangled with a hand towel and lying cold, and since that towel bore the name of Suma’s XX Inn where Brother had been staying, the detectives from the Metropolitan Police Department took Brother into custody as a suspect.”

Having spoken up to this point, the young lady gently wiped her face with a handkerchief.

“What did your brother say about the hand towel?”

Toshio asked.

"My brother stated he has no recollection of where he dropped it."

“When did Mr. Saito come to your house?”

“He came about six months ago, but my father was very fond of him.”

“Where is Mr. Saito now?”

“As a witness, he went to the Metropolitan Police Department with my brother.”

“Where is the professor’s body?”

“It was taken to the university’s forensic medicine department.”

“Do you have a microscope at your house?”

“There is one my father used.”

“In that case, first allow me to see the professor’s remains, and then I will visit your residence.”

As soon as the young lady left, Toshio called the Metropolitan Police Department and summoned “Uncle P”—that is, Detective Oda.
Although Dr. Endō’s case was not under Detective Oda’s jurisdiction, through his arrangements, we were able to view the professor’s remains.
Carrying the blood test equipment and that detective’s bag, the two of us went to the forensic medicine department, where Detective Oda had arrived ahead of us and was waiting.

Dr. Endō’s corpse lay in the autopsy room, covered with a white cloth in preparation for the afternoon autopsy. Toshio removed the white cloth, bowed respectfully, then ran his hands over various parts of the body. A deep ligature mark encircled the neck, while a faint trace of dried blood clung to the entrance of the right nostril.

Presently, Toshio withdrew a ruler from his pocket and began measuring the professor’s facial hair. The mustache formed a magnificent jet-black figure-eight, grown to its full length. Though no beard extended from chin to cheek, dense stubble—jet-black hairs under three millimeters—covered the lower face, evidence of unshaven days during his illness. Toshio meticulously measured these short bristles and recorded the results in his notebook. He then gave the figure-eight mustache a gentle tug, plucked two or three strands with precision, and carefully preserved them.

Once the beard examination was complete, Toshio meticulously inspected each finger one by one, eventually using tweezers to extract one or two extremely fine hairs from under the right index fingernail, which he preserved in the same manner.

“This should suffice.”

Toshio said with a satisfied expression.

Detective Oda enjoyed watching Toshio’s detective work, so he joined us in stopping for lunch along the way before we headed to the professor’s residence in Sugamo.

Upon arriving at the professor’s residence, Toshio announced that he would circle around the house and started walking ahead.
By the kitchen entrance, there were traces where a large amount of snow had been removed for some purpose.
Toshio stared fixedly at it, but soon started walking again. When he had circled around to the entrance, the young lady came out from inside the house to greet him.

“Please show me to the professor’s bedroom.”

Toshio said to the young lady.

In the bedroom stood a bed with a futon draped in white cloth, but Toshio removed these and carefully searched the bedsheet.
Then he retrieved a single hair from beneath the pillow and preserved it.
He proceeded to examine beneath the bed and throughout the bedroom, but no noteworthy findings emerged.

“Please show me to the bath area.”

Toshio suddenly said.
We exchanged puzzled glances, but the young lady silently led the way.

“Is Granny the one who heats the bath?”

Toshio asked.

“No, since Granny is elderly, the bath is Mr. Saito’s responsibility.”

“Is Granny really that old?”

“Her hearing is poor and her eyesight isn’t very good, but we’ve kept her on because she’s served us faithfully for many years.”

the young lady answered.

The bath area measured about two tsubo in size, with a bathtub roughly three shaku by four shaku installed in one corner, though it was damp with water. After an intense search, Toshio discovered a single small reddish-black stain on an inconspicuous outer section of the bathtub and asked Miss to scrape off that portion of wood along with the stain.

When the bath inspection concluded, Toshio requested the young lady to lend him the microscope. She then guided us to Dr. Endō’s study and produced the instrument. After she departed,

“Brother, first please examine under the microscope these hairs that were between the professor’s fingernails.”

Since Toshio had instructed, I promptly placed the hairs on a glass slide and positioned them under the microscope. When I looked, they were hairs shaped like field horsetails as shown in the diagram—I had never seen such hairs before.

“Toshio, I can’t figure this out. Take a look.”

I said.

Toshio examined it for some time, then smiled quietly.

“Did you figure it out?”

And I asked.

“I’ve got it! It’s bat fur!!”

“Huh? A bat?”

Detective Oda and I inadvertently shouted in unison.
Bat fur on the corpse's hand!! Now, what could this signify?

Suspicious Phone Call

Toshio then requested that I examine under the microscope both the beard hairs plucked from Dr. Endō’s corpse and those that had fallen on the bed.

When I took out two hairs and examined them under the microscope, the one from the corpse had a hair root attached, its tip—that is, the free end—split into three or four branches like a tree limb as shown in Figure A. The one from the bed, while nearly identical in length, bore scissor-cut marks at both ends as depicted in Figure B.

Toshio peered into the microscope and said with satisfaction.

“Brother, the hairs on the bed were from a fake beard.”

“Huh? A fake beard?”

I asked in surprise.

“That’s right. Hairs cut at both ends with scissors don’t grow on living humans... Now, go check the bloodstains on the bathtub—if it’s human blood, we’re set.”

To determine whether bloodstains contained human blood, one could examine the shape of red blood cells within them, but a more reliable method involved dissolving the stains in saline solution and observing whether mixing them with a substance called "precipitin" caused sedimentation.

Precipitin referred to a substance produced by repeatedly injecting human blood into rabbits, which caused their blood to develop components that formed white precipitates when mixed with human blood. The rabbit's blood would then be collected, its serum separated and preserved in glass tubes to prevent decay.

First, I placed a small amount of warmed saline solution onto a glass dish and dissolved the bloodstain from the board that Toshio had scraped off, using a thin glass rod. Then, I took out the precipitin I had brought with me, transferred a small amount into a slender test tube, and after approximately fifteen minutes, when I added the dissolved bloodstain solution to the precipitin, a white precipitate appeared immediately.

With just this experiment alone, I still could not definitively assert that it was human blood. This is because bloodstains from animals closely related to humans—that is, simians—also produce the same precipitation. However, distinguishing between human and simian blood would be difficult to perform unless we returned to our laboratory. In this case, since it was hard to imagine simian blood being present in the bath area, I deemed it acceptable to conclude it was human blood.

While I was conducting the above tests, Toshio searched every corner of the study. He opened desk drawers and rummaged through them, took out books from the shelves and shook them. Finally noticing Maruzen's "Daily Tear-off Calendar" hanging beside the bookcase next to the desk, he picked it up for some reason and began scrutinizing it fervently until he suddenly exclaimed, "I found it! I found it!"

Toshio's voice had been so loud that Uncle P—Detective Oda—standing beside me was startled and inquired.

“What happened, Toshio?”

“This is what shortened Dr. Endō’s life.”

“What is it?”

“It’s the secret of the poison gas!”

Toshio said triumphantly.

“The culprit who killed Dr. Endō seems to have searched this study quite thoroughly intending to seize the secret he had discovered.”
“However, true to form, Dr. Endō didn’t commit the blunder of hiding it in places like the safe, desk drawers, or books.”

“Dr. Endō had written the secret of the poison gas manufacturing method across four or five pages in the late December section of Maruzen’s ‘Daily Tear-off Calendar’ here.”
“Since calendars are delivered at the end of December every year, Dr. Endō must have intended to rewrite it once the new calendar arrived.”
“No one would ever think that a great secret was written inside a calendar whose pages are torn off every day.”
“That’s precisely where Dr. Endō’s brilliance lay.”
“That’s why the culprit ultimately failed to find it.”

After saying this, Toshio put the "Daily Tear-off Calendar" into his pocket.

"I'll be borrowing this calendar for the time being. Since we'll catch the culprit with this, you mustn't carelessly talk to others about it... By the way, Brother, how did the bloodstain test turn out?"

Toshio looked at the white precipitate in the test tube and said.

“As I thought—it’s human blood.”
“Alright, Brother—have Miss come here for a moment.”

As soon as Miss Yukiko entered the study, Toshio asked.

“When was the university supposed to start?”

“It starts on the 21st of this month.”

“During the recess, did Dr. Endō visit the university?”

“No, he remained secluded at home.”

“When you returned from Suma last night, did you approach the professor directly?”

“No—approaching him when irritable would have provoked him further, so I remained standing at the bedroom entrance.”

“You mentioned the bedroom was dimly lit?”

“Father disliked sleeping in brightly lit spaces.”

“Wasn’t Dr. Endō’s voice different from usual?”

“It was slightly hoarse, but that must have been due to his illness.”

“Did Dr. Endō shave his face every day?”

“He was not particularly fond of shaving.”

“When was the most recent time he shaved?”

“It was the morning of the 11th when he took to bed. That evening, since there was a meeting, he reluctantly shaved.”

“When was the bath prepared?”
“It was the evening of the 13th when I went out to call Brother.”
“But when we examined it earlier, wasn’t it wet?”
“That is because every morning, the live-in student Mr. Saitō takes a cold water bath.”

Toshio pondered for a moment and asked again.

"Does Dr. Endō have any relatives?"

"There is one uncle."
"He is my father’s younger brother and should currently be in Korea."

"What does he do?"

"It seems he isn’t engaged in any regular work."
"He himself says he’s a Korean rōnin."

"He seems quite an eccentric compared to Dr. Endō, doesn’t he?"

“He’s quite an eccentric. He takes delight in carrying things like a cane wrapped in snake skin, a coin purse made from toad hide, and a seal fashioned from wolf teeth.”

Toshio's face suddenly lit up with apparent delight.
At that moment, Detective Shirai from the Metropolitan Police Department entered, bringing along a young man.
The young lady looked at the young man,
"Oh, Mr. Saito—what has happened to Brother?"

she asked.

Before the live-in student Saitō could answer, Detective Shirai spoke.

“Mr. Nobukiyo still cannot be released yet. I have come to ask Miss a few questions.” Having said this, he looked at Detective Oda.

“Mr. Oda, what brings you here?”
he said.

“I’m Toshio’s guide.”

“Well, Toshio, good work there.”

Detective Shirai said to Toshio in a scornful tone.

“I’m here at Miss’s request. By the way—what were the autopsy results?”

Toshio asked.

“The cause of death was strangulation, I hear.”

“That’s been clear from the start.”

Toshio laughed and turned toward Saito.

“Mr. Saito—I hear Dr. Endō was in a terrible mood last night?”

“He was in a terrible mood.”

“Was it you who went to call Mr. Nobukiyo around one o’clock?”
“It was me.”
“Did Dr. Endō have a fight with Mr. Nobukiyo?”
“They were arguing about something.”
“I went to bed earlier, so I don’t know the details.”
“Who found the professor dead this morning?”

“The maid.”

“What about the maid?”

At this point, the young lady interjected, reporting that the maid, shocked by the professor’s death, had taken ill and was now resting in the back.

“Brother, come here for a moment. I need you to run an errand.”

Having said this, Toshio gave a meaningful glance and left the room, so I followed after him.

When we arrived at the entrance, Toshio spoke in a low voice.

“Brother， sorry about this—I need you to go hide in the storage room behind the telephone office now． I’ll head to the study to discuss this calendar．”
“Then， someone will surely come to make a phone call．”
“Then， listen to what number they call， who they summon， and what they talk about． Write it down on this paper and bring it back—though it’s fine if you can’t make out the conversation itself．”

I took the paper and pencil and， just as instructed， crouched in a corner of the dim storage room， straining my ears to await whoever might come to make a call．
One minute， two minutes， three minutes—in times like these， a single minute feels like an hour．
The surroundings were utterly still， and I could even hear my own heartbeat．

When about ten minutes had passed, the sound of the telephone room door opening quietly could be heard.

“Oote 3257.”

The voice that called out was unmistakably that of Saitō, the live-in student.

“Hello? Is this Tsutaya in Tōri 4-chōme? Please call Mr. Aoki.”

After a while, Saitō began saying something, but with his coded language, I couldn’t make out what he was saying at all.
After talking for about three minutes, he quietly closed the door again and left in that direction.

Thereupon, I exited the storage room, wrote down what I had just heard on paper, and entered the study.
And then, Toshio came out,

“Brother, good work there.”

As he said this, he took the slip of paper from me, glanced over it, jotted something additional, and passed it to Detective Oda.

“Uncle P, I’m sorry, but I need you to go run an errand now.”
“The details are written here.”

Detective Oda would comply with anything Toshio said.

“Well then, Mr. Shirai, I’ll be taking my leave now.”

Having said this, Detective Oda left.

Korean rōnin

After Detective Oda left, the five of us—Detective Shirai, Toshio, the young lady, the live-in student, and I—fell silent for a while, exchanging glances with one another, until at last Detective Shirai addressed Toshio in an unsettled voice.

“Toshio, have you identified the culprit?”

“Oh, but didn’t you say the culprit was Mr. Nobukiyo?”

Toshio said with a mischievous look.

“As for what counts as evidence… it’s just that hand towel, you know…”

“Then how about gathering more evidence?”

“That’s why I came to ask about the motive for the crime.”

“So it’s about inheritance? If Dr. Endō were to pass away, the property would naturally go to Mr. Nobukiyo, wouldn’t it?”

“I want to ask if there were any recent circumstances suggesting someone desired that property.”

“Miss, what do you think?”

Toshio said.

"My brother has a weak constitution and never went out anywhere for leisure. Under Father's orders, I had been sending him 150 yen monthly, but he couldn't even use up that amount."

After giving this answer, the young lady continued responding to Detective Shirai’s questions while meticulously recounting her brother’s gentle nature, until finally Detective Shirai—

“Hmm, so then the motive for the murder really was the secret of the poison gas, I suppose.”

he said.

Toshio paid little attention to the lengthy exchange between Detective Shirai and the young lady, occasionally taking out his pocket watch to check it as he fidgeted restlessly, but when exactly thirty minutes had passed since Detective Oda’s departure, he suddenly exclaimed in a loud voice,

“Mr. Shirai, please let Mr. Nobukiyo return quickly.”
“Now, Mr. Saito—Mr. Nobukiyo isn’t guilty, is he?”

Toshio said.

“I don’t know.”

The live-in student said, looking slightly flustered, but Detective Shirai was also startled by Toshio’s voice,

“Why?”

he asked.

“Why? Mr. Shirai—because the professor wasn’t killed last night.”

“What?”

Detective Shirai was astonished, but we too were left dumbfounded by this unexpected revelation.

"At least three days have passed since the professor was killed."

“What?”
“What?” said Detective Shirai.

“Ha ha ha, there’s no need to be so startled. So Mr. Nobukiyo—who returned last night—couldn’t have killed him, could he?”

“Where’s your proof?”

Detective Shirai said breathlessly.
Then, Toshio grew even calmer,

“Far from it—I even know who the culprit is.”
Toshio exclaimed.

The young lady and the live-in student stared intently at Toshio’s face.

“Who?”
said Detective Shirai.

“Everyone, please listen carefully.”
“The one who killed Dr. Endō is a beardless man with a hoarse voice who wears a scarf made by stitching together bat fur in winter.”

“Oh, then it must be my uncle!”
“But Uncle is supposed to be in Korea!”

the young lady exclaimed.

At that moment, Saitō, the live-in student who had been nearby, turned and fled.

As Toshio pointed and shouted “There!”, I lunged at the live-in student and grabbed him, but he resisted with desperate fury.

“Mr. Shirai, please handcuff Saitō immediately—Saitō is an accomplice.”

Detective Shirai, though flustered, proceeded to handcuff him as Toshio instructed, whereupon Saitō hung his head with a deathly pale face.

Just then, Detective Oda, who had left earlier, came back in panting heavily.

“Toshio, we caught him without any trouble.”

Detective Oda said happily, wiping the sweat from his brow again and again despite it being winter.

“That is most appreciated.”

With these words, Toshio approached Saito.

“Mr. Saito, this pains me to say, but you must answer for the crimes you committed. Now confess everything! I hear Mr. Aoki of Tsutaya—no, rather, the young lady’s uncle—has been arrested as well.”

Saitō kept his eyes shut and said nothing.

“Very well,” Toshio said.

“If you won’t confess, I’ll recount the full story of your crimes in your place. In other words, you repaid Dr. Endō’s kindness with betrayal.”

“Having become henchmen for Dr. Endō’s brother—the Korean rōnin—on the night of the thirteenth when Miss was dispatched to Suma, the two of you strangled the bedridden professor, placed his corpse in the bathtub, packed it with snow fetched to prevent decay, then last night when Miss and Mr. Nobukiyo returned, transported the corpse beneath the bed where Uncle—wearing a fake beard—impersonated the professor atop it, feigning anger to keep Miss at bay. After summoning Mr. Nobukiyo alone, dimming the lights and hiding half his face, you shouted at him to provoke a quarrel. Once Mr. Nobukiyo retired, you placed the corpse on the bed and—opportunistically seizing the hand towel he’d dropped—attempted to wrap it around the professor’s neck and frame him.”

“Right? That must be how it was. The Korean rōnin had become a foreign spy and tried to steal vital state secrets. But heaven does not side with villains! Even after going to the trouble of killing the professor, you never did manage to find the crucial secret of the poison gas, did you?”

“While the young lady was away, taking advantage of the old maid’s senility, you two must have searched every corner of this house frantically, starting with the study. However, since I ended up taking it instead, you must have felt regretful and, forgetting the danger, went to call the mastermind. And you must have discussed something like killing me and stealing the secret around tonight.”

“That was simply the end of your luck. Thanks to this, we’ve effortlessly arrested major traitors, kept vital secrets from falling into foreign hands—long live the Empire of Japan!”

“There you go, Mr. Shirai—now you’ve got yourself a proper memento too,” Toshio said. “Now hurry up and take Saito away so we can release Mr. Nobukiyo.”

Detective Shirai—who had been listening to Toshio’s astonishing explanation in a trance—suddenly came to his senses. With hurried bows to the others, he prodded Saito along and rushed out.

In the end, Uncle P—that is, Detective Oda—the young lady, and the two of us remained in the study, making four in total.
The young lady gently wiped away tears mingled with sorrow and joy and said.

“Mr. Tsukahara, thank you ever so much.”
“Though my father’s death brings sorrow, with my brother’s name cleared and the vital poison gas formula kept safe, I can rest easy now.”
“This is all thanks to you.”

“But what a terrible person Uncle is!”
“I was truly shocked.”
“But how on earth did you know it was Uncle’s doing?”

Toshio said triumphantly.

"It was the professor's beard that solved this case."
"No, not the professor's handlebar mustache, but the short beard along his jaw and cheeks."
"Though the professor fell ill on the 11th, when I observed his face, I was surprised by how little his beard had grown."
"Since people rarely shave while ill, even if he had shaved on the morning of the 11th, I reasoned that by last night it should have grown much longer."

So I took out a ruler and measured the beard hairs; they were all around 1.5 millimeters long, with not a single one exceeding 2 millimeters.
Since beards grow approximately 0.5 millimeters per day, if the professor had been alive until last night, his beard should have been at least 2.5 millimeters long.
So I concluded that the professor had not been killed last night.

When I considered this and concluded that the person in the professor’s bed last night had to be an imposter, I searched the bed and found a single fake beard hair. Assuming it was a substitute, I understood why he had shouted to keep Miss away. As Nobukiyo had not seen his father’s face in a long time—and especially in the dimly lit room—he failed to discern that it was an imposter.

Now assuming it was an imposter, I realized this man must be Professor Endō’s killer—and simultaneously concluded that Saito had to be his accomplice. Then, what would be the motive for the murder? It went without saying that they intended to steal the secret of the poison gas. The culprits likely remained until last night because they had presumably failed to find the secret. Having reached this conclusion, I searched the study and indeed found that the secret had been hidden there.

Next, I considered that if he had been killed three days prior, where had they hidden the corpse during that time? Then I remembered seeing a large amount of snow piled near the kitchen entrance before entering this house.

They had likely taken the snow to keep the corpse cold. When I deduced that they must have packed the corpse with snow in the bathtub and conducted a detailed inspection of the bathroom, I found a single bloodstain. That bloodstain was probably from the professor’s nose. There must have been others too, but Saitō likely washed them away under the guise of taking his cold baths.

Finally, I considered who the man impersonating the professor could be.
I reasoned that the person acting as the professor’s double must be a man who closely resembled him. When I inquired whether he had any relatives, Miss replied that he had an uncle—an eccentric who favored objects made from snake skin and toad skin.

At that point, I recalled the bat fur caught between the professor’s fingernails and reasoned that he must have been wearing a scarf made of stitched-together bat skins—a practical choice for winter.
When the killer strangled the professor and he resisted, the bat fur must have entered his fingernails at that time.
“Indeed, my deductions were correct.……”

Mr. Nobukiyo was acquitted that day.
As Toshio had deduced, the mastermind was Dr. Endō’s younger brother—who confessed to receiving a large sum from a certain foreign power, bribing Saitō the live-in student, and murdering the professor to steal the poison gas formula.
They hadn’t fled immediately after killing him both because they still hadn’t found the secret and because they schemed to cast suspicion on his son while covering their own tracks.

Thus, thanks to Toshio, the vital poison gas secret was not stolen.