The young medical student Klaus Bach has married the love of his life, Irene, and lives with her and their eternally screaming offspring in a small one-room apartment in his parents' house. So things are tight and everyone's nerves are on edge. What's more, the parents' well-intentioned advice is seriously disrupting the young couple's marital bliss.

"Route Casanova" is how people call the train driver Roland Diesler, as a love awaits him at almost every station. His colleague even has to carry out a plan extra so that there are no collisions between his rendezvous. However, when Roland looks at Ulla, the daughter of the station manager Bünau, this and father Diesler step in. They change the rosters of the two turtle doves so that they cannot see each other. But can the young couple be stopped by it?