The three of them headed downstairs one after another, making a beeline for the fifth-floor laboratory.

Pushing open the guest bedroom door, Sun Ya and Wei De squeezed in first to check on the rat cages.

Su Jin unplugged his phone from the power bank; the device was running slightly hot.

He was still tapping the screen when Sun Ya's voice rang out, laced with pure horror: "Another one is missing! Rat number six is gone... the cage is intact. No breaches."

Su Jin's brow furrowed. He opened the video logs to check.

"Ignore the cage for now. Let's watch the tape."

The two elders snapped their attention to the phone, exchanged a grim look, and locked their eyes back on the screen.

Su Jin bumped the playback to double speed.

In the footage, the rats behaved normally until the timestamp hit the thirty-five-minute mark.

The rat marked with a painted '3' began moving erratically, aggressively tailing another rat.

Two minutes later, its mouth opened.

Every hair on Su Jin's body stood on end!

On the screen, Rat number 3's jaw unhinged normally at first, but then the corners of its mouth violently split open, the horrific tear extending all the way down to its midsection!

Viscous strands of tissue and gore stretched across the gaping fissure, revealing a twisted, dripping cavern of flesh. It swallowed its cage-mate whole in a single, unnatural gulp.

Having inhaled a prey of its exact size, Rat 3's body bloated to twice its original mass.

It took over ten minutes for its grotesque anatomy to compress back to a normal shape.

Su Jin lowered the phone, his muscles entirely rigid.

Sun Ya and Wei De simultaneously stared at Rat 3 in the physical cage. It looked perfectly mundane, sending a violent shudder down their spines.

Just as Su Jin opened his mouth to speak, a rapid, violent pounding erupted from the floor below.

Muffled shouts and frantic cursing echoed through the concrete walls.

The three men flinched, their heads whipping toward the door.

"You two, get back to your rooms. I'm checking it out."

Su Jin decisively snatched up his tactical bag and shoved the phone inside.

He sprinted out of the apartment.

Taking the stairs three at a time, he vaulted down to the third floor.

The racket was pouring out of Room 302. Su Jin kicked the barricading sofa aside, drew his gun, and shoved the door open.

The moment the door swung wide, he was greeted by the sight of Li Kai and Cao Chengping violently tearing at each other's throats.

Spotting Su Jin, the two men froze instantly.

Before Su Jin could demand an explanation, Cao Chengping dropped to his knees and slid forward. He pointed a trembling finger at Li Kai, sobbing, "Boss! He's gone insane! He turned into a monster. He murdered Li Fang!"

"Bullshit!" Li Kai roared, his eyes bloodshot with rage. "You killed her! You waited until my back was turned and strangled her! You've lost your mind. I know what you..."

Cao Chengping immediately cut him off: "He drank the rainwater! He drank the rain and went rabid, Boss. He's just pretending! Kill him now!!"

Su Jin planted his boot into Cao Chengping's chest, kicking him flat on his back. He backed out into the hallway, his gaze turning to absolute ice.

"Nobody moves. On your feet. Now."

The two survivors shut their mouths, paralyzed by the sheer malice in his voice.

"Back up!"

They shuffled backward in terror. Su Jin stepped into the apartment and systematically cleared the angle to the bedroom door, peering inside.

Li Fang was sprawled awkwardly across the mattress, completely unresponsive.

A pillow lay discarded beside her head. A quick visual assessment suggested suffocation.

Having seen enough, Su Jin backed out of the unit entirely.

Up on the landing between the third and fourth floors, Wei De and Sun Ya were leaning over the railing, peering down at him.

Sun Ya kept his voice to a whisper. "Little Su, wasn't this block completely cleared? Did a Zombie wander in?"

"You can stay up there and watch, but keep your distance and stay behind me," Su Jin ordered coldly. "Three people, one dead. One of these two is exactly like that rat. Looks like we've got a live one."

Wei De and Sun Ya exchanged a sharp glance and hurried down a few steps, eager to get a better vantage point.

They had literally just discovered a brand new variant of the infection!

The host's internal structure and psyche mutated, manifesting a natural, predatory aggression towards other living creatures, yet possessing the terrifying ability to blend perfectly among their own kind.

They hadn't expected a human subject to present itself so immediately.

This was a golden opportunity for observation. They needed to dissect this situation completely.

Su Jin ground his teeth.

He leveled the muzzle of his gun at Cao Chengping. "Start from the beginning. Give me the exact timeline."

Cao Chengping flinched, babbling in a panic, "Just now. Literally a minute ago, Li Kai suddenly collapsed on the floor."

Su Jin and the two professors listened with clinical precision, scrutinizing the micro-expressions of both men.

When he finished, the muzzle snapped over to Li Kai. "Your turn."

"Boss, do not listen to his bullshit! He did all of this! He suffocated Li Fang!" Li Kai gestured frantically, desperate to be understood. "He woke up from passing out and just snapped! I wasn't paying attention, and he just lunged at her..."

Their stories were mirror images of each other, and neither man's panicked expression revealed any obvious lies.

Su Jin glanced back over his shoulder at Sun Ya and Wei De.

Both professors shook their heads, their faces grim.

They couldn't tell. The Disguised Infected was an impeccable actor.

Given that level of cognitive camouflage, there was no logical reason for the infected to commit murder right under Su Jin's nose.

The only pragmatic explanation was that the killer had just undergone the mutation.

Their core nature had been overwritten, and upon waking from the initial infection, their ravenous instincts had bypassed their conscious control.

Su Jin narrowed his eyes, his gaze slicing back and forth between the two suspects like a scalpel.

Finally, he waved the barrel of his gun at them.

"Both of you, strip. Everything off!"

"Boss..." Cao Chengping wailed miserably. "It really wasn't me! Is this actually necessary?"

Li Kai didn't utter a single word. He just started ripping his clothes off.

The two elderly experts immediately zeroed in on Li Kai with academic intensity.

Soon, both men were standing completely naked, shivering as Su Jin conducted a ruthless visual sweep of their bodies.

Normal. Everything was completely standard. They looked utterly indistinguishable from a regular human.

"Pull it back. Roll it up," Su Jin commanded, gesturing vaguely with the gun.

"Roll. Roll what up?" Cao Chengping stammered, trembling. He glanced sideways, only to realize Li Kai was already obliging with his foreskin.

"Boss, I'm circumcised. There's nothing to roll."

"Turn around!" Su Jin barked.

They inspected their backsides. Still, no anomalies.

A bead of sweat trickled down Su Jin's forehead. "Get on your knees!"

The two men abandoned all dignity and complied, kneeling with their backs to him.

"Spread your cheeks."

"Boss... please let me go. Stop tormenting me, I'm begging you!" Cao Chengping cried out hysterically. "I shouldn't have cursed you out earlier! I was wrong..."

Li Kai's jaw was clenched so tight his teeth ground together. He turned his head, staring at Cao Chengping with tear-filled eyes radiating pure murderous intent.

Su Jin and the two esteemed professors were currently conducting a highly focused study on a dual black hole system.

A shrill scream suddenly pierced the stairwell!

Su Jin spun around, his nerves wired tight. To his utter disbelief, Fu Qingdai was standing on the landing behind them.

Both her hands were clamped desperately over her face.

"Qingdai! Who the hell told you to come down here?!" Su Jin demanded furiously.

"I didn't see anything!" Fu Qingdai squeaked, her voice muffled by her hands.

"I didn't ask you that! Why are you down here?" Su Jin roared. "Get back upstairs!"

"Lunch is ready. My mom sent me to get you guys. I saw the floor was empty..."

While Fu Qingdai was still frantically trying to explain, a chaotic stampede of footsteps echoed from the floors above.

Fu Hu practically tumbled down the stairs, his face etched with panic, gripping his bow. Zhang Wan was right on his heels.

And incredibly, trailing behind Zhang Wan was Cheng Du, casually holding a wine bottle, alongside a completely bewildered Sister Liu.

The cramped stairwell was instantly logjammed with people.

But the second the crowd looked down at the scene below, they collectively turned to stone, as if struck by a bolt of lightning.

"Who authorized you all to come down here?! And you, Cheng Du! Weren't you ordered to quarantine in your room? Do you want to be kicked out?!" Before Su Jin could even open his mouth, Sun Ya exploded, glaring daggers at Fu Hu.

Fu Hu swallowed hard. "I heard my daughter scream, I panicked..."

Cheng Du's eyes darted erratically toward the naked men on the floor. He licked his lips. "I... I also heard the noise. I thought something was wrong, so I ran out. Who knew I'd walk into... Ahem."

"This is not a joke. One of these two has been infected. All non-combatants, fall back to your rooms immediately!" Su Jin barked, raising a hand to herd them away.

"Who's infected?" Cheng Du asked, his eyes wide. "They both look pretty normal to me."

Su Jin's gaze locked onto Cao Chengping. He raised the muzzle of his gun. "I already know exactly who it is. I'll brief you later. Back to your rooms. Now!"