Customs investigator Kressin returns from a Mediterranean cruise. Shortly before Hamburg, tour guide Ben Canitz behaves suspiciously. The next morning, Kressin reads in the newspaper that Canitz has been found dead in a canal in Hamburg. He gets involved in the police investigation and comes across a gang that is smuggling large quantities of drugs into Germany.

Two serious criminals have been caught abroad. The German police pick them up and transport them to Cologne in a special compartment of the Nordexpress. The gang, led by their boss Sievers, plans to kidnap the two. Members of this gang replace the locomotive driver and train staff with their own people so that they can safely stop the Nordexpress at a location of their choosing. Customs investigator Kressin, on his way back from Denmark, where he was dealing with porn smuggling, is on the train. He manages to prevent the kidnapping of the serious criminals.