Gaston (Guy Marchand has been married to Madeleine (Marie-Christine Barrault) for twenty years, and though they are a normal couple, both have an underlying, unexpressed interest in a non-monogamous life. Gaston's older brother Pierre (Jean-Marc Thibault) is married to a sensual, younger woman, Yvette (Annie Jouzier), and he is driven crazy with worry about her ability to stay monogamous. Finally, Gaston's friend Victor (Roland Giraud) appears to be a carefree bachelor, but in truth, he longs for monogamy. Seen from all sides, no one is really satisfied, and everyone thinks the other has it best. Nearly all of them opt for a change but soon discover that even with a change, their problems have not disappeared.