Luise is celebrating her 19th birthday on her father's luxury yacht on Sunday. Her father is the commodity trader, Peter Rehstahl. His son Michael unexpectedly appears on the boat with guests. Together with the German banker employed by Rehstahl & Co., and his lover Valerie, who owns a gallery in London, they agree to join the party and partake of the champagne offered them. After a bit of initial small talk, the father and son come into conflict because of financial matters and the lively mood is slowly and imperceptibly altered. Then at sunset as Michael, in a fit of rage, brings up the subject of a relationship between his father and sister Luise, no secret is safe. A long night begins, during which the struggle for truth and morals ensues.