Bai Jin reflected: A’Jin had last seen Madam Yan at noon. Adding the time it would take to walk back and forth between Madam Yan’s courtyard and Yan Qing’s location, plus the half hour A’Jin had waited outside after Yan Qing arrived, Madam Yan’s time of death should fall somewhere between noon and two in the afternoon.

“Go relay this information to E’Yuan.” Yan Qing said to one of the officers standing nearby.

The officer entered the forensic examination room. E’Yuan was in the midst of conducting the autopsy when the officer relayed the information. His expression faltered. “You say the time of death was between noon and two o’clock?”

E’Yuan’s own assessment of the body was consistent with this window. What he couldn’t understand, however, were the reddish marks on the body.

Earlier, during his preliminary examination at the scene, he had mistaken them for livor mortis. But now, after separating the epidermal layer, he found that these reddish marks were not livor mortis at all — they were injuries resembling burns.

“Understood.” E’Yuan nodded.

Once the autopsy was complete, E’Yuan wrote the autopsy report in two copies. One he handed to Bai Jin; the other he took personally to Yan Qing.

Yan Qing sat in the interrogation room. When the door opened and a familiar figure walked in, she recognized him immediately.

“Sister-in-law.” Bai Jin’s face and voice were filled with boundless remorse when he saw her. “Sister-in-law, I’m sorry you’ve had to endure this.”

Seventh Brother had instructed all of them before he left — no matter what, they were to ensure Yan Qing’s safety. And now, not only had they failed to protect her, they were forced to question her in this cramped interrogation room.

Yan Qing smiled. “I understand procedure. There’s nothing to apologize for — just follow the rules.”

After Bai Jin sat down across from her, he personally poured her some water. “Sister-in-law, have you had lunch? Are you hungry? I’ll have someone go buy you something to eat. Seventh Brother said you love little snacks — what would you like? Did you sleep at all? If you’re tired, go rest first.”

Yan Qing found herself at a loss between laughter and frustration. “Squad Leader Bai, I am currently a suspect, not a guest of the Military Police Division.”

“All right.” Bai Jin sighed. “Then I’ll begin.”

“Go ahead.” Yan Qing struggled to suppress her smile.

Bai Jin spread open his record book. “Name — I don’t need to ask that, I’ll fill it in myself.”

Yan Qing let out a laugh. Without waiting for Bai Jin’s questions, she spoke of her own accord: “This noon, I was in Father’s courtyard looking after him. Madam Yan sent someone to fetch me — I assumed it was regarding the division of property. When I arrived at the Madam’s courtyard, I did not find her in the sitting room, so I went into her bedchamber. The moment I entered, I saw the Madam lying in a pool of blood. I stepped forward to check her pulse — she was already dead. Just as I was about to call for help, I was struck on the back of my head. The sharp pain knocked me unconscious. When I next came to, I saw the maid standing nearby; her screaming brought the Yan Family members.”

As she spoke, Yan Qing turned the back of her head toward Bai Jin and parted her hair. “This is the wound left from the blow. It hasn’t broken the skin, but it has already swollen.”

Bai Jin looked at it and immediately called out toward the door: “Someone come!”

When an officer entered, Bai Jin quickly instructed: “Go buy some medicine for reducing swelling and dispersing bruising.”

“It’s only a slight swelling — it will go down on its own.” Yan Qing knew her own injury well. The attacker had only wanted to knock her unconscious, not kill her, and would naturally have controlled the force of the blow.

“I promised Seventh Brother I would not let sister-in-law come to any harm. And now…” Bai Jin let out a long breath. “I have let Seventh Brother down.”

“These past few days I’ve been distraught over Father’s illness — I didn’t think I might be framed. And you are not gods; you cannot protect me every moment.” Yan Qing said reassuringly. “Catching the real killer will be enough to clear my name.”

“Sister-in-law is right. We will definitely catch the killer.” Bai Jin said with some difficulty. “However…”

“I know.” Yan Qing said. “I was actually planning to come to the Military Police Division recently — I just couldn’t bring myself to leave Father’s side when he’s ill. Now, given this situation, my status as a suspect means I can’t return to the Yan Mansion anyway. This is actually a good opportunity — there’s something I want to do.”

Bai Jin’s round office was filled with laboratory equipment, including several newly imported pieces from abroad. Not just in Bei Di, but across the entire country, they were at the forefront.

When it came to scientific and technological infrastructure, Shi Ting had always been remarkably far-sighted.

“Sister-in-law, whatever you want to do, I will support you fully.”

Yan Qing said: “Yan Qin wasn’t entirely wrong — the Military Police Division is a symbol of law and justice in Shun Cheng. We cannot bend the law for personal gain. If it truly reaches the Inspection Bureau, Director Xie won’t overlook it out of past favors. I’ll stay here without special treatment. Whatever I need, just have Director Gu bring it to me.”

While Bai Jin felt this was an injustice to Yan Qing, in the current situation — with the Yan Family watching like hawks — if they were given any handle to grab onto, it would only work against Yan Qing.

“Right, sister-in-law — here are the statements given by the Yan Family members. See if you spot any inconsistencies.” Bai Jin handed her the file folder.

Yan Qing smiled. “Showing a suspect the witness statements — procedure really has gone out the window.”

“There’s no one else here. Read freely.”

Yan Qing had barely finished reading the statements when E’Yuan walked in.

“Master, the autopsy report is ready.” E’Yuan handed the report directly to Yan Qing.

Yan Qing said with a smile: “With Seventh Brother and Officer Zheng away, Bai Jin is acting as full commander of the Military Police Division. Shouldn’t you give it to him first?”

Bai Jin snatched the report from E’Yuan’s hands and personally delivered it to Yan Qing: “Sister-in-law, I can’t make heads or tails of this. You’re the professional — you look it over and explain it to me afterward.”

Yan Qing shook her head with a helpless smile. When had a suspect ever been asked to review the forensic report on behalf of the medical examiner and the squad leader?

Still, she had been eagerly awaiting the autopsy results, so she accepted it without ceremony.

“Scalp hematoma, epidural hematoma, cerebral contusion, cerebral edema…” Yan Qing murmured. “The cause of death was repeated strikes from a blunt instrument. How many blows were struck in total?”

This was something Yan Qing had once taught E’Yuan to assess, and he could now judge with practiced confidence: “Based on the trajectory of the fracture lines, the deceased sustained a total of four impacts to the head. The strike locations were concentrated almost entirely on the right occipital region — very focused — and the force applied was considerable.”

Yan Qing nodded: “Based on the strike positions, the killer’s height should be roughly comparable to the deceased, perhaps slightly taller — somewhere between one hundred sixty-two and one hundred sixty-seven centimeters. The killer had strong hands — very likely someone with martial training.”

E’Yuan said: “Both of those characteristics don’t match your conditions, Master.”

“These are only inferences drawn from the body. They cannot serve as exculpatory evidence — people have unusual qualities, and scene conditions are endlessly variable.” Yan Qing’s gaze settled on a row of text. “Burn injuries to the deceased’s neck and chest… are these fresh?”

E’Yuan acknowledged: “When I examined the scene, I initially mistook them for livor mortis. Later, after comparing against the time of death, I confirmed those marks were not livor mortis. I performed epidermal separation and can confirm they are burn injuries. Based on the state of the wounds, they appear to have been caused by hot water.”

“And the scalp near the head wound — is there burning there as well?”

“I cleaned the deceased’s head wound, but the blood saturation made it impossible to determine whether burns were present there.”

Yan Qing stared at the autopsy report in her hands, momentarily lost in thought.

“Sister-in-law, do you think this burn injury has any bearing on the case?” Bai Jin asked from the side.

Yan Qing said: “You just showed me the Yan Family’s statements. The maid called A’Jin said that the last time she saw Madam Yan, the Madam asked whether the tea had been brewed yet. A’Jin brought in the freshly boiled tea before going to find me. Now, from the Madam’s courtyard to Father’s courtyard is a fifteen-minute round trip at minimum — and factoring in delays along the way, by the time I reached the Madam, nearly half an hour had passed since A’Jin brought in the tea. Half an hour is more than enough for tea to cool to lukewarm. If I had picked up the teakettle and struck Madam Yan with it, the water inside would not have caused burns this severe.”

E’Yuan and Bai Jin were struck with sudden realization.

E’Yuan said: “In other words, the killer struck shortly after A’Jin delivered the tea — while Madam Yan was not expecting it, the killer snatched up the kettle and struck her on the head. The still-scalding water splashed out and caused varying degrees of burns across the deceased’s body.”

Yan Qing nodded: “Furthermore, when the killer grabbed the kettle, she did not know it still contained near-boiling water. As she struck Madam Yan, the hot water would not only have splashed onto the deceased — it would have splashed onto the killer as well. Therefore, the killer’s hands and forearms must bear burn marks.”

Yan Qing instinctively glanced at her own clean, unmarked arms.

“Additionally, the killer must be very familiar with the Yan Mansion. She was able to enter Madam Yan’s room without being noticed — and after knocking me unconscious, escaped without alerting the maid. This person may not be living within the Yan Mansion, but she is certainly connected to it.”

“Sister-in-law, I’m going back to the scene right now. The killer couldn’t have come and gone without leaving a trace.” Bai Jin said. “I’m going to find whatever evidence that wretch left behind.”

Yan Qing smiled. “Go. And ask Director Gu to send me the equipment I need.”

“Master, I’ll head back and keep searching the body for clues.”

“Mm.”

Both of them bustled out at once.

Half an hour later, Director Gu had people bring several items into the interrogation room, which had now become Yan Qing’s workspace. Though she had no absolute certainty of success, it was still better than doing nothing.

“Director Gu, please help me purchase these items as well.” Yan Qing handed him a written list.

Director Gu looked at the materials on the list, blinking in puzzled confusion. “Sister-in-law, what are you trying to research?”

“Streptomycin,” Yan Qing answered. “I want to extract streptomycin.”

“Streptomycin? What is that used for?”

Streptomycin would not be invented until more than twenty years from now. For this era, it was an utterly novel and unfamiliar name. That Director Gu had never heard of it was entirely understandable.

Even for herself, the likelihood of successfully producing streptomycin was less than fifty percent.