Holger has been living separately from his wife Sigrid and their two daughters Silvia and Lara for some time. Every weekend he picks up 15-year-old Silvia at a party and brings her to the small terraced house in which he no longer lives. That evening, weeping Lara suddenly stands in the front door and tells her father that her rabbit Poldi, which Holger never wanted to buy, fell victim to a marten. Silvia insists on a proper funeral which Holger should attend and which will take place during the night for reasons of time. And so the four become a family again that night - for a brief moment.

Summer on Three Wheels is the story of the shy outsider Flake, who not only suffers because his parents named him after the stuttering keyboardist of a famous rock band. He also absolutely fails to confess his love to the girl he secretly yearns for and to assert himself against his rival. So Flake first makes the wrong decisions - and then to the drug dealer Kim and the embittered wheelchair user Philipp. A special kind of tour de force develops from this encounter: a road movie that leads in a Piaggio moped car at 45 km/h from the top of Stuttgart to Lake Constance.