A dead man lies in a Duisburg bus - apparently the accidental victim of a stabbing. The murdered man was the owner of a dance studio that he ran together with his wife, Manuela Prinz. The investigation reveals that the perpetrator is a Thai. But when the detectives track him down, they find another body. Everything indicates that the Thai committed suicide. Schimanski suspects that the aloof Manuela is not telling him everything she knows. But suddenly it is she who asks him for help: her husband's "business friends" have contacted her and threatened her life if she is not willing to secure further "deliveries".

Schimanski and Thanner are confronted with a case that happened a long time ago and that they were unable to solve: in 1978, one of the perpetrators was seriously injured during a bank robbery and was then executed in the bank by the leader of the gang. The perpetrators managed to escape - except for the Pole Zbiginiew Pawlak, who waited next to his dead brother until the police arrived. During the subsequent investigation, Pawlak was unable to say a word. The press then nicknamed him "Moltke", which he kept even during his prison sentence because he remained stubbornly silent.