The action takes places over a couple of days on a modest yacht on a lake in rural Poland. A middle-class couple invite a young hitchhiker to take a trip with them and at first the trio have a fine time, fussing with the sails, tanning on the decks. But, quickly, a competitive air comes to dominate, as the wife, bespectacled and dour in the opening scenes of the film, is transformed into a brown, intense beauty, gobsmacking in a bikini.