Chapter 20: SOS Under the Violet Light

The purple flashlight flickered in the dim room as Cen Lian continuously moved it around. Tang Hua carefully traced the areas on the glass that had once been stained with fluorescent agent.

“It seems to stop here,” Qi Yan observed from the side.

Tang Hua looked around and indeed found no further traces of the fluorescent agent.

“After six years, the chemical’s color has faded quite a bit,” Cen Lian said from a distance, shining the purple light over the marked area again. “It looks like three English letters.”

“That’s SOS,” Qi Yan said with certainty.

Having observed the remaining fluorescent shapes as a bystander, he had sketched the pattern in his notebook, which became clearer once the last trace was confirmed.

“I’m going to test the fluorescent agent on the window next to this one,” Tang Hua said and left without hesitation. “If this SOS was meant to be seen at night, it should be visible from downstairs.”

Cen Lian watched him leave to fetch the materials.

“If the fluorescent traces can indeed be seen from outside, then it explains why Sun Xiaoyu suddenly appeared in the third-floor inpatient ward,” Qi Yan closed his notebook. “But how did the culprit ensure that only Sun Xiaoyu could see the SOS distress signal?”

Cen Lian was pondering the same question.

He stood by the window and suddenly noticed that behind the inpatient building there was only an old-looking structure, isolated from any street or outpatient building.

“Director He, what’s behind this building?” Wang Yuanteng, catching Cen Lian’s pleading glance, immediately asked the balding middle-aged official surnamed He.

Director He glanced in the direction Cen Lian was facing and answered without hesitation, “That’s the dormitory building. Our hospital’s resident trainees and visiting doctors who don’t want to rent apartments live there.”

“Did Sun Xiaoyu live in the dormitory back then?” Cen Lian came over.

Director He recalled and nodded quickly. “I remember among the few girls who went straight into residency training without graduate school, she was the only one who lived far from here, so she stayed in the dorm.”

“Is there direct access from the dormitory to the inpatient building?” Cen Lian pressed further.

Director He pointed downstairs, “There’s a small door on the first floor — it’s a shortcut just for them.”

---

Cen Lian recalled the time of the incident from the case files and glanced back at Qi Yan.

Qi Yan came over as well.

“The incident happened after 10 p.m. According to the shift schedule, Sun Xiaoyu would have come out of the dormitory intending to take a shortcut through the inpatient building directly to the outpatient clinic,” he gestured the distance. “The damage to this ward back then might not have been accidental.”

Cen Lian had already mentally reconstructed the method of the crime. Once Tang Hua returned with the materials, it would be easy to verify if the SOS signal could be seen at night from the dormitory route to the inpatient building.

But the most crucial question now was not the method of the killer, but how to find clear evidence pointing to Lin Xiangyuan.

...

Tang Hua soon arrived with several ultraviolet-reactive reagents borrowed from the criminal police lab, accompanied by a technician.

The technician studied the window with a UV light for a while, then took out a tube of reagent.

“He used this kind of ‘invisible ink,’” the technician said, pulling out a brush and quickly painting the SOS symbol on another piece of glass with no prior marks, signaling them to observe from there.

Cen Lian and Tang Hua went downstairs and stood on the only path from the dormitory to the inpatient ward.

“Start,” Cen Lian called out remotely to Qi Yan.

Inside the third-floor ward, the technician stepped back as Qi Yan held the purple flashlight, shining it precisely on the glass.

“Can you see it?” Wang Yuanteng asked over the radio.

“Yes, I’m taking a photo for you,” Cen Lian said, holding up his phone and capturing the writing on the window clearly.

They had come to the hospital that afternoon, and although it was not yet half past ten, the sky was already quite dark, effectively simulating the environment on the night Sun Xiaoyu was attacked.

On the third-floor inpatient window, the line “SOS” was clearly visible under the UV light.

“Truly a meticulous plan,” Tang Hua looked up at the third-floor ward. “He must have designed this specifically. From the dormitory to the inpatient building, Sun Xiaoyu would only be able to see these few rooms.”

Cen Lian sensed something was off. “This ward shouldn’t have suddenly broken down and needed repairs.”

---

There are so many coincidences in the world, how could it be that just when Lin Xiangyuan needed to commit murder, the ward best suited to lure someone upstairs happened to break down and require repair?

“Check who stayed in this ward before the malfunction,” Cen Lian said as he headed upstairs, speaking into his radio to Wang Yuanteng, “I suspect this ward was deliberately sabotaged.”

Wang Yuanteng looked at the dormitory’s remote location and agreed that the ward’s damage seemed suspicious.

Director He from the medical office had sensed something from their conversation. Having worked in the office for nearly twenty years, his instincts told him that in a murder investigation, it’s best to let the police check whatever they want.

“We have the inpatient records here. I’ll take you to look now,” Director He became unexpectedly proactive.

As Cen Lian went upstairs, he saw Director He leading Wang Yuanteng to retrieve the hospitalization records.

“These are the photos we took downstairs,” Cen Lian showed the recently captured SOS to Director He and Wang Yuanteng after greeting them. “As long as the culprit knew Sun Xiaoyu’s dorm exit time for work, it would be very easy to ensure she was the only one to see this distress signal.”

Wang Yuanteng could clearly feel the case gradually unraveling and becoming clearer with every step.

“Let’s go check the inpatient records,” Wang Yuanteng said, pulling Cen Lian along.

Tang Hua glanced at Qi Yan and the technician guarding the ward and decided to join them in the room.

Cen Lian and Wang Yuanteng went to check the admission records.

“The last patients to stay in this ward before the malfunction were these three,” Director He said, pulling up records from before April 17 six years ago and quickly finding the admission records for the third-floor Ward 327.

“When the police came to investigate at the time, they specifically reviewed the surveillance footage. They also suspected someone deliberately damaged the oxygen system embedded in the wall, but no one unrelated to the ward was caught entering in the days before the incident,” Director He explained as he located the patient information.

“Please give us copies of these three patient files,” Cen Lian requested thoughtfully, “and expand the search to include all the wards with windows clearly visible from the dormitory path to the inpatient building. If the culprit wanted to intercept his premarital check-up report, given how urgent he was, he wouldn’t focus on just one ward.”

With a rare display of compliance for a middle-aged man, Director He personally handed the patient admission records to Wang Yuanteng.