Chapter 21

Chapter 21 2. Eden Lake-12

A few minutes later, Jiang Xiaoyuan returned, carrying a large cardboard box, puffing and panting.

Liu Yi quickly put on gloves, took the deceased’s pair of shoes out of the box, and without a word, flipped them upside down.

“…As expected.”

Seeing the soles of both shoes, Liu Yi let out a long, relieved sigh and slowly said these two words.

“What are you doing?”

Although Qi Shanyu didn’t understand, he trusted Liu Yi, knowing that although he often acted unpredictably, every seemingly meaningless move was to confirm some sudden inspiration.

The shoes in Liu Yi’s hands were the white sneakers taken from Su Ruirui’s body. Both shoes bore the Binhai Middle School emblem on the outer side, standard school uniform shoes, clearly worn for some time. The tongue of each shoe had the class and student number written in marker, verified to belong to Su Ruirui.

“Hm, how should I put it…”

Liu Yi pondered for a moment, then turned to his graduate student who had just run errands for him. “Xiao Jiang, come here.”

“Eh!”

Jiang Xiaoyuan, thinking his boss was sending him on another errand, immediately ran over without hesitation.

“Stop.”

Liu Yi gestured for him to pause, then said, “Turn backward.”

Jiang Xiaoyuan: “???”

Though confused, he obeyed, performing each command, then stood facing away from them.

“Now, take a few steps forward.”

Following Liu Yi’s instructions, the poor Jiang Xiaoyuan walked back and forth in front of Qi Shanyu like a spinning top, three times in total.

“Okay, that’s enough.”

Liu Yi called a stop, then looked at the police officer beside him. “Officer Qi, do you understand?”

If it were An Pingdong, someone who easily got along with everyone, he would probably have retorted bluntly. But Qi Shanyu, steady and polite by nature, shook his head honestly, “No, I still don’t understand.”

“Yeah, boss, what exactly are you doing?”

Jiang Xiaoyuan, completely confused after being used as an example and walking in circles in the lab, stepped closer in a humble, questioning posture.

“Look, every time Xiao Jiang took a step just now, unconsciously, he always stepped out first with his right foot.”

Liu Yi pointed at Jiang Xiaoyuan’s right leg.

“Huh?”

Jiang Xiaoyuan paused, instinctively stepped forward, and looked down—indeed, the right foot stepped first.

“Really is true!” he exclaimed, surprised. “I’ve never noticed this before.”

“In fact, most right-handed people also tend to favor their right foot in life—for starting, jumping, the first step is usually with the right foot.”

Liu Yi paused, then continued, “According to different lab statistics, about thirty to forty percent are exceptions. But whether right- or left-foot dominant, when acting unconsciously, the choice is basically fixed.”

He picked up Su Ruirui’s shoes from the table and flipped them over. “Not just for stepping or jumping, but in normal walking, weight distribution also tends to favor the dominant foot. Over time, the soles wear differently.”

Qi Shanyu examined the soles carefully, noting that the right heel’s inner pattern was almost worn flat, while the left heel showed about half as much wear.

“You mean Su Ruirui habitually favored her right foot?”

“Yes.”

Liu Yi nodded, then replayed the convenience store surveillance video that Qi Shanyu had recently obtained, dragging the timestamp to the moment Su Ruirui withdrew her campus card, picked up two plastic bags, and stepped forward.

From the overhead angle, it was clear—the first step was indeed with the right foot.

“But I remember…”

Liu Yi tapped the table lightly with his long fingers in gloves, then finished, “In the library surveillance, when ‘Su Ruirui’ stepped off the railing, the left foot led.”

“Hiss!”

Before Qi Shanyu could speak, Jiang Xiaoyuan drew a sharp breath. “Could this be… a double?”

“Mm, now it seems that possibility is quite high.”

Liu Yi returned the shoes to the box, smiling at Qi Shanyu. “I think it’s necessary to investigate students in Su Ruirui’s class with similar height and build.”

Qi Shanyu nodded, expression serious.

He hadn’t expected that just by coming to the institute, the investigation’s direction would take such a sharp turn with an unforeseen breakthrough.

“However, there’s one crucial thing. Without clarifying this, the investigation will be difficult.”

Qi Shanyu’s gaze fell on the dozen or so slides near the microscope, still pending diatom analysis. “That is, where exactly did Su Ruirui drown?”

“…”

Liu Yi didn’t immediately answer. He silently looked out the window at the sky divided into three sections by nearby buildings.

After a while, he removed his gloves, stood, and paced irritably, letting out a sigh. “I really don’t want to trouble that guy, but there’s no choice…”

Liu Yi turned to his graduate student. “Xiao Jiang, before the end of work, go to the evidence department, give them the drowning water samples taken from Su Ruirui’s stomach and duodenum, explain the case, and tell them we need it urgently.”

“Eh?”

Jiang Xiaoyuan’s eyes widened in shock and distress. “Boss, I’m just a rookie—how can I go straight to the head of the evidence department and ask for priority processing… and, and…”

He hesitated, then added, “The case is so complicated, I barely heard any details, I’m not confident I can explain it properly…”

“Tsk!”

Liu Yi glared at the pitiful Jiang Xiaoyuan unreasonably. “Fine, I knew I couldn’t count on you. I’ll go myself!”

He slapped the table, stood up, grabbed the labeled test tubes, and, wearing only lab slippers, stormed out the door.

With long, urgent strides, the hem of his white coat fluttered; his aggressive posture seemed less like seeking technical help and more like going to confront someone.

Qi Shanyu stood dumbfounded, watching Liu Yi’s brisk, determined retreat.

“Well…”

Only after Liu Yi’s footsteps faded did he timidly ask, “Does Director Liu have some grudge against the head of the evidence department?”

“N-no, I guess…”

Jiang Xiaoyuan’s mouth twitched in an awkward half-smile. “If I had to say, probably… like repelling the same polarity?”

&&& &&& &&&

“All right, lights off.”

Liu Yi nodded at Jiang Xiaoyuan, signaling readiness.

Jiang Xiaoyuan immediately flipped the wall switch. “Click”—the brightest ceiling light in the bathroom went out. With the windows already covered in black plastic, the room was plunged into darkness.

“Wow, incredible!”

An Pingdong leaned in the doorway, barely glancing, but could see the bathroom floor covered in blotchy blue fluorescence without explanation.

Mentally translating it into bright red blood, he muttered, “If I didn’t know this was a girls’ high school dorm bathroom, I’d have thought it was a knife murder scene.”

“Although no knife, it probably really is a murder scene.”

Liu Yi observed Jiang Xiaoyuan collecting blood samples, a faint smile on his lips. “After all, Su Ruirui likely died here.”

“But Su Ruirui drowned—where’s all this blood coming from?”

In the dark, An Pingdong couldn’t see Liu Yi’s expression clearly but detected the almost inaudible cold laugh in his voice.

“Probably nosebleed?”

Standing beside him, Qi Shanyu answered for his partner, “Su Ruirui’s nose was broken. This should be blood from her injured nose.”

“Mm.”

Liu Yi nodded. “Nasal fractures often damage the mucosa; severe cases can even cause cerebrospinal fluid leakage. This amount of bleeding is entirely possible.”

He pointed at the blue fluorescence on the floor.

This was the Luminol reaction.

Luminol reacts with hemoglobin to catalyze hydrogen peroxide decomposition, producing singlet oxygen, which oxidizes luminol to fluoresce. Even if cleaned, latent blood can be detected.

“Wow, you tech people are amazing!”

An Pingdong slapped Liu Yi’s back in the dark.

“If you hadn’t told me, I’d never have guessed Su Ruirui drowned in the toilet!”