"We found it in the victim's bedroom when we searched the crime scene. Since we couldn't find the victim's relatives at the time, the key was kept at the police station along with the victim's file."

“My sister gave me the key. And I’ve been to this house a few times since my sister’s accident. I remember, yes, I clearly remember that the window was closed the last few times I came here.”

"When was the last time you came here?" Wang Shen asked, his brows furrowed.

"I don't remember very clearly, it was three or four months ago."

"Who goes there!" Before Xu Xiaolin could react, Wang Shen rushed towards the door. A figure darted swiftly around the dark corner of the stairwell and disappeared downstairs. Wang Shen chased after him with all his might.

"ah!"

Wang Shen stopped in his tracks as Xu Xiaolin's voice rang out behind him. In that brief moment of distraction, the dark figure had vanished without a trace. Wang Shen stared in the direction the figure had disappeared, gritted his teeth, and gave up the chase. He retraced his steps and saw Xu Xiaolin sitting on the stone steps.

"Are you alright?" Wang Shen quickly ran a few steps to Xu Xiaolin's side.

"It's nothing, I just tripped and fell while running." Xu Xiaolin rubbed her ankle, her brows furrowed.

"Let me see." Wang Shen lifted Xu Xiaolin's ankle and gently twisted it a few times. "It's nothing, just a sprain. It'll be fine after a few days of rest."

"Was there someone outside the house just now?" Xu Xiaolin asked Wang Shen, enduring the pain.

“Yes.” Wang Shen fell into a brief moment of thought.

"Who is this person? Is he related to my sister's case?"

“It’s so late, unless someone lives here, who would come here? And the fact that he ran away as soon as he was exposed suggests that he’s probably involved in your sister’s case.”

"It's all my fault." Xu Xiaolin angrily punched her thigh.

"Don't blame yourself too much. The culprit will eventually show their true colors. By the way, sit here for a while. I still need to go back inside and check."

Xu Xiaolin nodded, and Wang Shen got up and went into Han Mo's room. Wang Shen turned on the light; the outline of the deceased drawn on the floor was still there. Wang Shen tried his best to recall the deceased's expression, movements, and posture before death. The deceased was sitting on the floor with a fruit knife stuck in his abdomen, his back against the sofa. Apart from the bloodstains around the deceased, there were no other bloodstains. This indicated that the deceased had not engaged in a fierce struggle with the murderer before death. Of course, all of this was based on the premise of homicide. Bloodstains? Right, Wang Shen suddenly thought of something and quickly walked to the balcony window. Wang Shen bent down and stared at the windowsill for a long time. The bloodstains that had been on the windowsill were gone! Someone must have returned to the house afterward and wiped away the bloodstains on the windowsill. But who was this person? The shadowy figure from earlier? It was hard to say for sure at the moment; it was just a very likely guess.

Wang Shen combined the details described that night by the garbage collector and the middle-aged woman to reconstruct the general events of that night. A man (let's assume he's the murderer) had a heated argument with Han Mo and then killed her. To cover up his crime, the man promptly disposed of the scene. To eliminate all evidence left in Han Mo's room, he packed up her belongings and threw them out of the balcony window. He probably didn't notice that some of the blood from his hands stained the windowsill. After cleaning up his tracks in Han Mo's room, the man left.

"No!" Wang Shen tapped his head. If this was truly the case, then how was the locked room created? And what about Han Mo's own phone calls to order food and to Zheng Wu? None of this could be explained. Based on the timeline, the man must have left before those two phone calls. We all know that dead people can't make phone calls. Was Han Mo still alive then? But if Han Mo wasn't dead, why would that man let her leave? And, logically speaking, shouldn't the first reaction be to call the police or an emergency services?

"Ah!" All the questions swirled in Wang Shen's mind. Before he could sort out a general idea, his thoughts were interrupted by a scream.