Since I became mentally ill, I've been much more spirited.

Upon arriving at the Municipal Bureau's Criminal Investigation Division,

Cao Cheng hadn’t even seen his second sister yet but was instead greeted by a room full of high-ranking officials.

They were all exceptionally warm when they saw the young tycoon.

After all, Cao Cheng was a local entrepreneur, the youngest self-made billionaire in the region, and an annual donor of various vehicles to the bureau—even funding an entire aviation squad.

Everyone knew it was all for Ren Fanxing’s sake.

This also meant Ren Fanxing was highly valued within the bureau—so much so that they were reluctant to let her transfer out.

After the usual round of pleasantries,

Second Sister finally appeared.

Don’t let her modest rank fool you.

She was one of the squadron leaders under the Special Operations Unit, sporting two silver stars on her shoulders—a rising star among the new generation of officers, decorated with countless awards.

That said,

Second Sister was still in plainclothes today—work requirements, after all.

"A day without you feels like three years, Second Sister. I’ve missed you so much." Cao Cheng pulled her into a big, enthusiastic hug.

It made Second Sister blush, especially with everyone watching.

But no one thought much of it.

Second Sister rapped Cao Cheng’s head lightly. "Let go."

As he released her, Cao Cheng muttered, "Limited edition."

Second Sister nearly hit him.

Just then,

A senior officer in a white dress shirt—the head of the criminal investigation division—spoke up.

After the earlier small talk, his tone turned serious as he addressed the real matter at hand.

"Mr. Cao, Captain Ren mentioned you have some experience with hypnosis?"

Cao Cheng suddenly understood.

So this was about hypnosis.

He nodded. "I know a little."

Second Sister then explained the situation.

They had recently apprehended a high-IQ suspect. While they had him in custody and some evidence, the chain of proof was incomplete.

First, several bodies were still missing.

Second, the murder weapon hadn’t been found.

The suspect was a mastermind—a serial killer responsible for multiple deaths, each time leaving almost no trace.

This time, however, he had slipped up—leaving behind a single drop of blood.

That one drop.

After months of pursuit and investigation, they finally caught him, and the blood evidence matched.

But that alone wasn’t enough.

The man was tight-lipped.

He also seemed well-versed in interrogation tactics, making the entire process frustratingly difficult.

Without a complete evidence chain, securing a conviction would be nearly impossible.

A few days prior,

Someone had brought up cases abroad—like Denmark in 1951, where a criminal was hypnotized into confessing.

Or the 1976 school bus kidnapping in the Netherlands, where a hypnotist helped the driver recall the buried license plate number, leading to the vehicle’s location through minor details.

Domestically, while there wasn’t much precedent, there had been cases where psychologists or hypnotists assisted in interrogations.

Not many.

But they existed.

After some discussion, they reached out to a renowned expert—a well-known hypnotist surnamed Shen, who happened to be in Zhonghai.

But the results were underwhelming.

The suspect’s high intelligence made him resistant to hypnosis—his subconscious fought back, making it nearly impossible to put him under.

In short, it didn’t work.

That’s when Second Sister thought of Cao Cheng.

No particular reason—just that Cao Cheng seemed to know everything.

Back when he was treating their eldest sister, he’d casually mentioned being "a little familiar" with hypnosis.

Second Sister knew exactly what his "a little" meant.

So she took a chance.

Why not try?

At this point, they had nothing to lose.

……

After hearing Second Sister’s explanation,

The surrounding officials began debating.

Some opposed using hypnosis—after all, it wasn’t scientifically validated, and who knew what side effects it might have on the suspect?

Not that side effects were the main concern, but it made them seem unprofessional.

They were trained in criminal investigation, in law enforcement—what would it look like to resort to hypnosis?

It’d be like hanging a portrait of Guan Yu in the precinct and praying to him before a mission.

Not exactly rigorous.

Others supported the idea.

With advancing technology and deeper research into psychology and hypnosis, new tools could aid investigations.

Like sketch artists or computer forensics—specialized roles existed for a reason.

Their job was to use every available resource to solve cases, no matter what.

As long as it helped complete the evidence chain, catch the killer, and bring closure to the victims, did the method really matter?

This case had dragged on too long—a serial killer, with the province and surrounding cities all watching closely.

To put it bluntly,

If not for that single drop of blood, they wouldn’t have been able to hold the suspect this long.

Right now, they were keeping him as a "key suspect," citing resisting arrest and assaulting officers during capture.

But that excuse wouldn’t hold forever.

……

Eventually,

All eyes turned to Cao Cheng.

Second Sister asked, "Well? Think you can do it?"

Even she wasn’t entirely confident.

She’d been sure at first—after all, Cao Cheng had bragged about his "little" hypnosis skills.

But now, at the critical moment, she wondered if she’d acted too impulsively.

Maybe she should’ve asked him privately first.

"Relax, it’s no big deal. I’ve got some confidence, but I’ll need to review the case files first. Ideally, I’d also see the suspect’s background—his life history, family, anything or anyone he particularly cares about…" Cao Cheng said.

Hearing this, Second Sister brightened.

An expert’s approach was telling.

The previous specialist had asked for the same things.

At the very least, it proved Cao Cheng knew what he was doing.

……

Soon,

The crowd of officials dispersed—everyone had their own work to attend to.

They’d only gathered earlier because Cao Cheng was there, a matter of courtesy.

Now, in a small conference room, Second Sister had the case files and all relevant materials brought in.

Incidentally,

Second Sister had a young female officer as her assistant, who addressed her as "Master."

"Little Uncle," she greeted Cao Cheng politely.

What manners.

Cao Cheng grinned, leaning slightly toward her. "What’s your name? How old are you? Got a boyfriend?"

"……" The girl flushed.

Second Sister’s expression darkened as she yanked Cao Cheng back. "Focus on the files."

Cao Cheng chuckled. "Hey, I’m just balancing work and leisure. I already skimmed some of it—can’t I take a break? Besides, I’m just making conversation, showing concern for my little niece. Right, little niece?"

He leaned toward her again, grinning.

Second Sister dragged him back once more, glaring as she hissed through clenched teeth, "Do you still want that limited edition?"

Cao Cheng immediately straightened up, adopting a solemn expression as he picked up the files.

Second Sister snorted in satisfaction.

The young officer stifled a laugh—this billionaire "uncle" was nothing like she’d imagined.

……

Cao Cheng soon immersed himself in the reading.

His eyes flew across the pages, devouring the stacks of documents covering half the conference table.

Second Sister had already summarized the case well, so now he was hunting for finer details.

After a while,

Cao Cheng concluded one thing with certainty:

This serial killer was undeniably mentally ill.

No question about it.

His victims?

All chickens.

Tortured to death.

Cao Cheng, having lived two lives, had encountered many such people both in reality and in films.

They seemed to harbor a natural hatred toward prostitutes.

Either their mothers were one,

or their wives were.

There were no other possibilities.

However, after his arrest, he never admitted to it, so naturally, no one could figure out why he had such a deep-seated vendetta against them.

What a lunatic!

Hmm.

Found it.

Found the suspect’s past records. At eighteen, after failing the college entrance exam, he had an extreme breakdown and underwent a year of psychiatric treatment.

The second time he retook the exam, he scored nearly 700 points.

A genius.

From then on, he turned his life around—a straight-A student.

Ever since he "got mental illness," he became a lot more spirited.

Later, he even became an outstanding teacher, specializing in math.

Huh!

Interesting.

In short, he had a history of mental illness.

But very few people knew about it, and on the surface, he showed no signs of it.

During the investigation, it was clear that those around him spoke highly of him.

His students saw him as a "kind and approachable" mentor.

His colleagues considered him a "easygoing" coworker who didn’t nitpick.

The principal and other leaders viewed him as a teacher who was "devoted" to his students, even to the point of "forgetting meals and sleep."

None of the classes he taught had poor math performance.

Even in his neighborhood—whether it was his next-door neighbors or the local convenience store—no one who knew him had a bad word to say.

That was rare.

This year, he was thirty-seven.

Unmarried.

His father passed away when he was twenty-nine—died of illness.

The first serial murder case occurred when he was thirty, eight years ago.

The first few cases were manageable—the bodies were always found.

Either in the river or in abandoned construction sites.

But by the fifth case, the body went missing. Though the disappearance of the prostitute was reported, and traces of blood were found in her residence, confirming she was likely murdered, the body was never recovered.

But there was a common thread: the victims shared the same profession.

All were sex workers.

All worked in the trade.

And all favored wearing red.

That’s why the cases were linked.

The most recent case happened earlier this year—another missing prostitute. At the crime scene, investigators found traces of blood that didn’t belong to the victim, meaning it was likely the suspect’s.

After further investigation, they finally zeroed in on the suspect.

This teacher.

Naturally, he was arrested. But during the arrest, he clearly lost his temper, scuffling with the police.

That counted as resisting arrest and assaulting an officer.

Plus, there was the blood evidence.

Otherwise, he wouldn’t have been held for so long.

……

Yet the suspect insisted he knew nothing about the crimes, had never been to the scenes, and had no idea how his blood got there.

Maybe someone was framing him.

After all, innocent until proven guilty.

No surveillance footage at the scenes either—meaning he’d done his homework.

The only thing tying him to the crimes was the blood.

No bodies, no murder weapon.

Hard to convict him.