In the late 1970s, on the steam train from Ningyang to Hacheng, young conductor Wang Xin diligently performed his duties among the bustling passengers. Mistaking the old railway policeman Ma Kui for a fugitive, they began an unlikely mentor-disciple relationship. From initial dislike to mutual respect, Wang Xin and Ma Kui fought side by side on the front line of railway public security. They tackled issues such as theft, abduction, drug enforcement, patrolling, and combating thefts and robberies, always prioritizing the safety of every passenger, and selflessly safeguarding the security of trains travelling between north and south. Wang Xin and Ma Kui passed on the torch of railway police across generations, witnessing the development of China's railways from steam locomotives to electric locomotives and then to high-speed trains, witnessing the rapid changes in China.