Lin Dongxue and Chen Shi brought the police to the gym and called all the employees for questioning. During the period, the gym manager showed them the snapped belt for the equipment that had broken at the time. Chen Shi put on gloves to check it. It had been cut by a knife.

Xu Xiaodong brought over an employee and the employee said, "I haven't seen the person you mentioned, but a thin man kept smoking on the stairs that day."

"Which staircase?"

"It's the safe exit one."

The employee brought them there. There was a safe passage behind the gym. In fact, you could enter the gym directly from this staircase, but climbing the stairs was too tiring and few people came from here.

The employee got to the platform separating the stairs, pointed to the floor, and...