Ace Anderson and Dick Kowalski are two semi-competent cops in San Francisco during the late 1970s. They show more attention towards appearing cool and disco dancing, but finish the cases by the end of the day. They are assisted by their disgruntled police chief Captain Dobbs, plucky reporter Miss Lee, and fellow disco lover Boogaloo.

Sent by his father, Sébastien gets to know an old uncle, Captain Louis Maréchal, a fishing-boat operator, in his mansion at Morsant. He meets Jonathan and Clarisse who work in the household of Sophie-Virginie, the daughter of his uncle's business partner. Little by little, he learns the secrets behind his uncle, a former resistance fighter who lost his wife and his son 25 years ago, time stopping for him in January 1943. In the light of the different stories he hears, Sébastien first blames him but then shows understanding and affection for his old uncle.