Zhang Lin quickly learned that the problem in the operating room was with the oxygen tank.

The incident happened so suddenly that Zhang Lin didn't think such a large hospital operating room wouldn't have prepared something like an oxygen tank, so this matter seemed strange no matter how you looked at it.

After leaving the doctor's office, Zhang Lin told his two colleagues to keep an eye on the situation in the operating room, while he took the elevator down to the hospital floor's monitoring room.

"Hello, please help me retrieve the surveillance footage of the neurology department corridor and the second-floor operating room from 2 PM yesterday to now."

After the security guard saw Zhang Lin's work ID, he retrieved all the surveillance footage.

Zhang Lin sat there himself, watching the screen bit by bit.

First, it showed the oxygen tanks being delivered to the operating room. Each department has a fixed number of oxygen tanks. The surveillance showed that a specialized person delivered the oxygen tank in the corridor. On the way, they met a male doctor who helped deliver it together, and then they came out together. After that, no one went in until the surgery.

These two were the last to have contact with the oxygen tank, so he had to ask them to clarify the situation.

Watching the surveillance video of the operating room, Zhang Lin began to watch the video surveillance of Zhao Di's corridor.

Everything seemed normal at first, but when he saw a figure appear in the corridor surveillance video at four o'clock in the morning, when there was basically no one in the corridor, Zhang Lin's heart pounded. There was indeed someone in the corridor last night.

Unfortunately, the position of the camera was a bit far, so it couldn't capture the person's features, even their clothing was blurry.

The person in the video walked very slowly, hesitated for a while at the corner, then quickly turned and walked towards the stairwell, disappearing into the darkness of the stairwell. The person walked so lightly that they didn't even trigger the sound-activated lights in the emergency exit.

Half a minute later, Zhang Lin himself appeared in the position where the person had been.

Although he knew that someone appeared in the video at that time, it didn't necessarily mean that the person was related to Zhao Di, but Zhang Lin still wanted to see who it was.

He also checked the surveillance at the main entrance, but that was a bit difficult. After all, there were four main entrances, and the other party might not leave immediately. Perhaps, in order not to be discovered in the surveillance, they would deliberately dawdle on the floors. When they got to the first floor, there would be more people, and it wouldn't be so easy to identify them.

Zhang Lin was afraid that the other party was using a diversion tactic last night, so he didn't dare to chase after them, so he didn't know if the other party went downstairs immediately. To be sure, he could only use a clumsy method, checking the surveillance of every floor below the neurology department, just to see if anyone came out of the stairwell during that time.

However, after checking until after seven o'clock in the morning, he didn't see anyone coming out of any of the stairwells.

Just when Zhang Lin was about to give up, a familiar figure suddenly appeared in the video. Although the other person was walking towards the entrance with the crowd, Zhang Lin still recognized Bai Ma Shan at a glance.

He pulled the mouse back and found that Bai Ma Shan first appeared on the second floor. The surveillance position on the second floor was different from the other floors and couldn't capture the stairwell, so Zhang Lin couldn't determine whether Bai Ma Shan came up or down the stairs.

In the video, Bai Ma Shan was protecting his right arm with his left hand, and his right hand seemed to be injured.

Zhang Lin stared at Bai Ma Shan as he came down from the elevator on the second floor and walked directly out of the main entrance on the first floor.

And more than ten minutes later, Wu Peng and Jia Wenjun's family walked in from the main entrance on the first floor.