Bernard is a teacher in the suburbs and lives with Victoria. Didier is a wealthy Parisian pharmacist and is married to Murielle, Victoria's sister. While the former drives a rusty car, the latter drives a black Mercedes. Both brothers-in-law are complete opposites and hate each other. During dinner, Didier and Bernard make a bet: to stop Tobacco smoking for fifteen days, until the next family get-together. The first days go off like a dream and both are on top of the world. But things quickly turn sour. Didier and Bernard find it harder and harder to resist the temptation. They become irritable, suspicious, they lie; until the fifteenth day: the family get-together. They have kept their word, but relations between them and their wives are at an all-time low. Despite this, they are both determined to remain non-smokers.