Wang Shen pushed his chair further into his desk, then his gaze fell on the row of cabinets against the wall. He remembered the diary Lin Su had mentioned. Wang Shen tiptoed to the glass cabinets and gently opened one of the doors. Inside were thick file folders, each labeled with a patient's name. Song Mu was very skilled at organizing files. The files were arranged alphabetically by the first letter of the surname, from top to bottom and left to right. Wang Shen noticed this pattern and began searching for Han Mo's name based on it.

Wang Shen searched through all the files but found no record of Han Mo. Oh, and the diary from last time was nowhere to be found either. Wang Shen stared at the cabinet in front of him, then suddenly crouched down. The cabinet probably wasn't custom-made, as there was a sizable gap at the bottom. Wang Shen leaned down and peered into the gap. Sure enough, a file folder lay quietly in the dark gap at the bottom of the cabinet.

Wang Shen pulled the file folder out from the gap. The cover of the folder bore the name Han Mo. Wang Shen opened the folder and carefully examined the records concerning Han Mo inside. All of Han Mo's consultation times and processes were completely preserved in this file. Han Mo suffered from severe depression, her experience of being raped by Zheng Wu during her adolescence, and even witnessing Han Shuang's murder by Zheng Wu, were all documented. From this perspective, Song Mu was probably the person who knew Han Mo best.

Wang Shen flipped through the files one by one, slowing his movements when he reached the last one. The last sheet wasn't a file, but an extremely ordinary piece of paper. A few lines were written on it, seemingly a poem: "Meeting is difficult, parting is even more difficult; the east wind is powerless, the flowers are withered..." Looking at the poem, Wang Shen began to speculate about the relationship between Song Mu and Han Mo. He pulled the paper out separately and compared the handwriting with Song Mu's handwriting in the previous files. Wang Shen confirmed it: it was indeed the same person's handwriting.

Wang Shen photographed Han Mo's file for his records, then carefully put all the documents back into the file folder. Finally, he stuffed the folder back into the dark crevice. Wang Shen crouched down again to examine the gap under the glass cabinet. Apart from the diary, Wang Shen had found almost all the information about Song Mu in Song Mu's office.

"Dr. Song, you're back." The secretary's voice came from outside the office. Unexpectedly, Song Mu really appeared at this moment.

"Okay." Song Mu responded simply and decisively.

"Dr. Song," the secretary called out.

"Is there anything else?" From Song Mu's tone, it was clear that he was somewhat impatient.

"Your friend has arrived and is waiting for you in the office."

"My friend?" Song Mu's tone revealed surprise. He didn't continue talking to his secretary, but strode quickly to his office and forcefully pushed open the door.

"Who are you?" Song Mu stopped and looked at Wang Shen, who was sitting in the guest chair.

"Dr. Song, it's great to finally meet you in person." Wang Shen smiled as he stood up from his chair, walked over to Song Mu, and shook hands with him warmly.

"Who are you?" Song Mu stared at Wang Shen with a stiff expression.

“Dr. Song, there’s no need to be nervous.” With that, Wang Shen placed his police ID in front of Song Mu. “I’m only here to ask you about Han Mo’s situation and to learn about the recent cases.”

Song Mu glanced at Wang Shen's identification, his expression remaining largely unchanged. He placed his briefcase on his office chair and said casually to Wang Shen, "Please sit down." Then, Song Mu turned and walked to the water dispenser, poured himself a cup of water, and handed it to Wang Shen. Song Mu remained calm and unhurried, not in a hurry to speak with Wang Shen. Instead, he returned to his desk, picked up his own cup, poured himself a glass of water, and took a few sips.

"I didn't expect Dr. Song to be left-handed." Wang Shen looked at Song Mu holding the cup with his left hand and noticed that all the stationery on the desk was placed on the left side, so he came to this conclusion.

"Officer Wang's insight is truly remarkable." Song Mu took two more sips of water and then placed the water glass on his left.

"No wonder. Dr. Song is so outstanding and capable. That's why they say left-handed people are generally more intelligent." After saying that, Wang Shen smiled and took a sip of water.