Bus driver Zhou Ning is operating normally, passenger Zheng Guixiang misses her stop, family members Zhao Gang and He Li make a ruckus in the carriage and seize the steering wheel, causing more than half of the bus body to hang outside the overpass guardrail. After the crisis is resolved, the involved family members turn black into white. In order to cover up the problem of using refurbished and scrapped parts for vehicles, bus company supervisor Sun Zhicheng tries to tamper with evidence and make Zhou Ning take the blame. Multiple passengers step forward to testify, and the investigation team digs deep, uncovering a major dark secret of scrapped safety parts flowing into bus, school bus, and hospital shuttle fleets. All relevant responsible persons are held accountable, and Zhou Ning is cleared of wrongful grievances and returns to his position.