While on duty at the highway toll station, toll collector Shen Zhixia notices that a black SUV reveals anomalies everywhere. The woman inside the car, Zhou Lan, knocks on the car door to pass a cryptic signal, the statements of the man and woman contradict each other, and the rear wheels of the vehicle bear abnormal weight. Even without conclusive physical evidence, Shen Zhixia still decisively triggers early warning and blocks the lane. After the police arrive, several searches reveal no obvious problems, but Shen Zhixia does not relax her vigilance, digging deep along the clues to uncover the case of Shengheng Testing Company illegally transferring hazardous radioactive source equipment, preventing the spread of major safety hazards. The relevant personnel involved in the case are investigated according to the law, and Shen Zhixia also receives work treatment where merits and demerits coexist.