After Jochen saves police officer Erich's life, the two men become close friends and Erich helps Jochen get a job working for Berlin's local train system. But Jochen falls into the hands of the beautiful West Berlin agent Ellen, who convinces him to participate in acts of sabotage against the trains. All of a sudden, Jochen is making a lot more money and even Erich's former girlfriend Inge becomes interested in him. But everything begins to unravel when Erich observes his friend's illegal activity on one of his nightly rounds.