According to the investigation by Hu Jia and others, Fan Ya Fu and Cai Yun were taken directly from the city bureau back to the prison.
They did not stop the car at all during the journey. So, this period of time can be almost ruled out.
Hu Jia checked the prison's entry and exit records. Fan Ya Fu returned to the prison at 10:48 AM.
After returning to the prison, Fan Ya Fu went to the office to handle handover procedures with the detention cell. This process was not short, as it involved filling out documents and identifying Zhang Hang.
According to Fan Ya Fu's signed identification form, the time was 12:03 PM.
Then, they escorted the prisoner back to the cell. The identification area was about 500 meters away from the prison. Fan Ya Fu arrived at the detention cell at 12:08 PM.
For 500 meters, it is perfectly reasonable for two people to take 5 minutes.
After the handover, Fan Ya Fu went to the cafeteria to eat. This time was difficult to pinpoint and the process was hard to investigate, but a detail can be used to judge: the prison broadcast began at 12:30 PM, and someone saw Fan Ya Fu coming out to wash dishes when the broadcast started.
This means that the time of Fan Ya Fu's murder was between 12:30 PM and 1:30 PM.
Fan Ya Fu was with Zhang Hang Jiang before entering the cafeteria, but not during mealtime. But who would choose to exchange information in the cafeteria?
Moreover, the people in the cafeteria said that Fan Ya Fu was sitting alone.
Therefore, the other mole contacted Fan Ya Fu after 12:30 PM.
Then the problem arises: Lü Qing Qing discovered that Liang Ying Zhang was beaten at around 11:00 AM.
Adding the time for information transmission, plot arrangement, and searching for Liang Ying Zhang, Fan Ya Fu must have transmitted the information before 10:00 AM, or even earlier.
But during that time, Fan Ya Fu was still on his way back to the prison, or even at the police station.
This means that Fan Ya Fu did not transmit the message after returning to the prison, but had already acted at the police station.
However, as a escort, Fan Ya Fu had to stay close to Zhang Hang Jiang at all times, and there were others like Ou Yang Wen around him. How could he have had the opportunity to transmit information?
"But if it wasn't him, then who else?" Li Yang asked.
"Then who else was there that day?" Hu Jia countered.
"Cai Yun!" Both said in unison.
...
The investigation into Cai Yun was very simple, it only required knowing if he had left the city police station alone that day.
Ou Yang Wen provided a definitive answer to this.
It turned out that after Hu Jia and the others left, Fan Ya Fu took Zhang Hang Jiang to handle the procedures. Cai Yun was not with them during this period.
Logically speaking, as a escort guard, Cai Yun should have been present throughout. But such minor matters were not usually scrutinized, so Cai Yun not completing the entire escort did not attract anyone's attention.
Later, Hu Jia went to see Tang Bing. Tang Bing said that the person on duty that week was someone else, but because he had injured his leg, Cai Yun had voluntarily switched shifts.
Furthermore, during subsequent interviews, Hu Jia discovered that all the tasks, such as "identification" and "escorting back to the cell," were performed by Fan Ya Fu. This implied that Cai Yun had spare time to arrange the crime scene.
"So, the mole we are truly looking for is Cai Yun," Hu Jia finally breathed a sigh of relief. Although there was no definitive evidence to prove Cai Yun was the killer, it was still better than the previous blind groping.
This completely confused Ou Yang Wen. How did the suspect change after a trip around?
After listening to Hu Jia's analysis, he had to sigh that it was brilliant, truly brilliant.
Of course, this "brilliance" referred to Cai Yun.
If the killer was indeed Cai Yun, then knowing that transmitting information would arouse Hu Jia's suspicion, he chose to frame someone else first.
Only by killing Fan Ya Fei, who was with him, and then faking a suicide scene, would the police believe that Fan Ya Fei committed suicide out of guilt.
Not only would he successfully shift the blame for being the "mole," but more importantly, he would save his own life.
However, he miscalculated that the time was too tight, leaving no room for Fan Ya Fei to breathe. This, instead, became the reason for Fan Ya Fei's acquittal.
But now that the suspect was identified, where was the evidence?
Troublesome!
...
"Then we only have to search everyone's room again. Before, we mainly checked if there was any damage to the room or bloodstains on the floor. This time, we will search the wardrobes."
Hu Jia thought of a method. The range of the killer was certain: all prison guards. And prison guards have uniforms when they are on duty. Almost everyone here, apart from their underwear, would not have other clothes.
And the prison guard uniforms are limited, two sets each for spring, summer, autumn, and winter, with different styles.
Whose wardrobe was missing a uniform would be the most suspicious, because he had already disposed of the blood-stained clothes.
"Yes! Why didn't we think of this method earlier?" Li Yang, overjoyed, immediately conducted another thorough search of all personnel's dormitories.
Of course, searching everyone's room was just an excuse. He actually wanted to search Cai Yun's room.
He would search with everyone else to lower the suspect's guard.
Unfortunately, Cai Yun's wardrobe had all eight sets of clothing. This made Li Yang somewhat dejected. Had he guessed wrong again?
...
Seeing Li Yang walk out of his dormitory looking very disappointed, Cai Yun smiled and said, "Take care." After he closed the door, the smile on his lips instantly vanished.
He sat back at his desk, took out a few photos from the drawer, and his eyes gradually turned fierce.
Is this really forcing me to my death?
He knew that the photos sent by the other party were a final ultimatum. If you don't expose yourself, your whole family will be safe. If you are exposed, choose the correct path.
Cai Yun dared not gamble. Facing a butcher, he had no courage to gamble.
Since the target was locked, investigating the case became much easier. Hu Jia had meticulously tracked Cai Yun's movements from his return to the prison until he reappeared in front of everyone.
Most of the time, Cai Yun was not present, including when "Fan Ya Fu" was on the rooftop.
After "Fan Ya Fu" jumped off the building, Cai Yun rushed to the scene, wearing pajamas, claiming he was taking a nap.
Cai Yun's dormitory had not revealed any problems in the first two rounds of searches. So, it was clear that the primary crime scene was not in the dormitory.
But if the crime scene was not in the dormitory, and it was confirmed to be in the dormitory building, then where else could it be?
"Could it not be on the rooftop?" This was Ou Yang Wen's question. After all, he had not participated in the investigation of this case initially, so his thinking was broader.
"But there were no bloodstains or signs of struggle on the rooftop," Li Yang raised his objection.
"What if there was no struggle? Did Cai Yun have no way to kill Fan Ya Fu? As for the rooftop, there are many possibilities for no bloodstains," Ou Yang Wen retorted.
Right!
All along, they had been stuck in a loop, who said that murder must involve a struggle? A sudden heavy blow to the head could also cause the victim to lose consciousness instantly.
"So, think about it, why was Cai Yun taking a nap? Why was he wearing pajamas when he came downstairs?" Ou Yang Wen posed another question.
"Because his clothes were stained with blood." Li Yang's eyes lit up, but then dimmed. "But we searched his room, and we didn't find any blood-stained clothes there."
"No! That's because we missed a detail," Hu Jia said, looking up: "The trick of substitution!"