Bus driver Li Shuang noticed an abnormality in the last bus's brakes and insisted on suspending service, but she was blamed after a vehicle-moving accident. During her investigation, she uncovered shoddy parts and irregular clearances, and revealed a decade-old cold case using evidence left behind by her father. Her father, Li Jianshan, was not driving under the influence, but was forced to drive a faulty vehicle, ultimately sacrificing his life to save all the passengers. Facing emotional blackmail and interference from vested interests, Li Shuang stuck to the safety bottom line, joined hands with Zhou Yan to find out the truth, brought those responsible to justice, cleared her father's name, and grew into a bus safety inspection team leader.