Some pain leaves indelible marks.

At 3:07 PM, Yu Yan stood in front of the office in the far corner on the third floor of the Provincial Public Security Department's Forensic Center and knocked on the frosted glass door. There was no response. He knocked three more times, this time with more force.

"Get in here." A hoarse voice came from inside, even more somber than last night.

Yu Yan pushed open the door, and was immediately greeted by a strong, bitter aroma of coffee and a chilling smell of disinfectant. Fan Jinci's office was unexpectedly tidy; everything was precisely arranged along some invisible grid. The office's occupant was currently slumped in a leather swivel chair, his pale face marked with prominent dark circles under his eyes, his hair disheveled as if swept by a typhoon. He wore a wrinkled white lab coat over his black silk pajamas—clearly, he hadn't changed since returning from the scene.

Most striking were the seven empty coffee cups lined up to his right and the gleaming scalpel to his left.

"The report is on the table. Take it and get out of here." Fan Jinci didn't even look up, his voice sounding like it was squeezed out from the depths of hell. He was observing something in front of a microscope, his slender fingers mechanically adjusting the focus, his knuckles turning white from the force.

Yu Yan didn't move. His gaze swept over the sofa in the corner of the office—the blanket on it was a mess, and several pillows were dented from being violently punched. It seemed someone really hadn't slept all night.

"I brought coffee." Yu Yan took a thermos from his briefcase. "Guatemalan Geisha, double espresso, no sugar."

Fan Jinci's fingers paused, and he finally looked up from the microscope. His eyes were bloodshot, with dark circles under them, but his gaze was still sharp enough to kill. "You investigated me?" Each word was like an icicle piercing his skin. —"

“Just a guess.” Yu Yan placed the thermos in the corner of the table, the only spot not occupied by coffee cups. “Seven empty cups, all filled with espresso residue. Either you’re extremely addicted to caffeine, or you’re trying to stay awake to finish something.” He pointed to the microscope. “Tissue samples from electroshock therapy?”

Fan Jinci's expression changed. He slowly straightened up, like a startled viper: "How did you know?"

"Just guessing," Yu Yan repeated, a slight smile playing on his lips. "Last night you specifically mentioned the stun gun, but the report only mentioned it in one line. That doesn't seem like the style of a legendary forensic pathologist."

Fan Jinci stared at him for a full ten seconds, then suddenly grabbed the thermos and gulped down a mouthful. His Adam's apple bobbed, and a trickle of coffee slid down his chin and disappeared into the collar of his pajamas. Yu Yan forced himself to look away.

"This isn't an ordinary stun gun," Fan Jinci finally spoke, his voice still hoarse but with a hint of life in it. "Military grade, modified. The voltage is three times higher than the civilian standard, but the electrode spacing is specially designed so it won't leave obvious burn marks." He pushed aside the microscope, pulled a stack of photos from the drawer, and slammed them on the table. "Look at this star-shaped scar inside the trachea; it was caused by a specially made electrode."

Yu Yan picked up the photograph; the close-up shot showed several tiny, almost perfect pentagram marks on the inner wall of the trachea. "Is this type rare?"

"Not domestically." Fan Jinci's voice suddenly became unusually calm. "The US special forces used it in small numbers between 2003 and 2005, codenamed 'Morning Star.' Its main purpose was..." His finger unconsciously traced his carotid artery, "...to keep prisoners conscious while rendering them unable to speak."

The office suddenly became eerily quiet. Yu Yan noticed that as Fan Jinci spoke, his left hand remained tightly gripping the scalpel, his knuckles turning white.

"You recognized it after only a few glances last night?" Yu Yan asked softly.

Fan Jinci's gaze drifted into the distance: "Some pain... leaves an indelible mark." His words were as soft as a sigh.

Yu Yan suddenly felt a strong urge to press for answers, but Fan Jinci had already stood up abruptly, his white coat billowing up like a cloak. He walked to the whiteboard on the wall, which was covered with photos of dismembered bodies and autopsy reports.

"This wasn't the killer's first offense." His voice regained its cold, professional tone. "The technique was too practiced. The order in which the body was cut, the way the internal organs were disposed of, even..." He pointed to a close-up of a cross-section of the spine, "He made the cut between the third and fourth lumbar vertebrae, the easiest place to dismember a body. An ordinary person wouldn't even know this detail."

Yu Yan walked up to him, their shoulders almost touching: "Do you believe there are undiscovered early victims?"

"I'm sure of it." Fan Jinci's profile was as cold and hard as a marble statue under the fluorescent light. "And..." He suddenly turned around, unexpectedly closing the distance between himself and Yu Yan, "The 'suspect' you arrested isn't the real culprit."

Yu Yan could smell the strong scent of coffee and a deeper hint of mint in the other's breath: "Why do you say that?"

"Because a real serial killer wouldn't make this kind of mistake." Fan Jinci's fingertip touched Yu Yan's chest, the heat scorching through the shirt fabric. "Dumping the body in an easily discoverable place? Using freezing to interfere with the determination of the time of death? Too deliberate. The killer is framing him."

Yu Yan looked down at the pale, slender hand and suddenly noticed a nearly invisible, thin scar on the inside of Fan Jinci's wrist, extending all the way into his sleeve. He instinctively grabbed the other's wrist: "What's this?"

Fan Jinci jerked his hand back as if burned, the scalpel already pressed against Yu Yan's Adam's apple: "Touch me again, and I'll let you experience the taste of 'Morning Star' too." His voice was dangerously soft.

After a few seconds of awkward silence, Yu Yan suddenly laughed: "Your hand is shaking."

"Shut up."

"A person who hasn't slept for thirty-seven hours has no right to threaten others with a knife." Yu Yan slowly and firmly pushed the knife away. "Sit down, tell me why someone who knows how to use a military-grade stun gun would frame an ordinary coffee shop owner, and then go to sleep."

Fan Jinci narrowed his eyes, seemingly assessing whether the man before him was foolish or brave. Finally, he took a step back, twirled the scalpel between his fingers, and precisely placed it back into the scalpel holder on the table.

"Because of the fun." He sat back in his chair, then suddenly slumped down like a deflated balloon, rubbing his temples with his fingers. "The real killer is enjoying the process... watching you arrest the wrong person, watching the media report it so much, watching..." His voice trailed off, eventually becoming a muttered monologue.

Yu Yan suddenly realized that Fan Jinci was struggling with extreme fatigue. He went around to the other side of the table and snatched the scalpel before the other could react.

"What are you doing—" Ci Jinfan suddenly looked up, a rare look of panic flashing in his eyes.

"Keep it safe." Yu Yan put the knife into his suit's inner pocket. "Now, lie down on the sofa and sleep for two hours. I'm going to re-interrogate the suspect."

"Give me--"

"This is an order, Forensic Pathologist Fan," Yu Yan's voice brooked no argument. "Unless you want the liver to be mistaken for a spleen at the next autopsy?"

Fan Jinci opened his mouth, seemingly wanting to retort, but in the end only let out a weary snort. He staggered to his feet and walked towards the sofa like a drunkard, almost bumping into a bookshelf along the way. Yu Yan subconsciously reached out to support his shoulder, feeling the protruding shoulder blade under the fabric.

"Stun guns..." Fan Jinci muttered as he slumped onto the sofa, "Check veterans from 2004 to 2006...especially those who were discharged..."

His voice grew softer and softer until it became even breathing. Yu Yan stood in front of the sofa, watching the usually arrogant, aloof, and unapproachable genius forensic doctor curled up in a ball, his black hair disheveled and falling across his forehead, looking almost... fragile.

Yu Yan quietly took the white coat from the hanger and covered Fan Jinci with it. Before turning to leave, he inexplicably reached out and gently brushed a strand of hair from Fan Jinci's forehead. Fan Jinci frowned slightly in his sleep, but did not wake up.

On the desk, the tissue samples under the microscope still gleamed coldly; the star-shaped scars resembled some mysterious constellation pattern. As Yu Yan gently closed the door, he recalled Fan Jinci's words:

"Some pain leaves indelible marks." He suddenly wondered just how deep those unseen scars on the chief medical examiner's body were.