Three young men (Jacques, Pierre and Michel) share an apartment in Paris, and have many girlfriends and parties (During the movie, we even learn that they have signed a contract never to allow a girl to spend more than one night at their place). Once, during a party, a friend of Jacques' tells him he has a quite compromising package (which turned out to be heroin) to deliver, and asks him if he can leave it discreetly at their place. Jacques agrees and, as he works as a steward, flies away for a one-month trip in Japan, telling Pierre and Michel about the package. Then, one of Jacques' former girlfriends drops a baby before their door, making Pierre and Michel believing it is the package they are waiting for. Their lives are then completely changed. This movie follows the bachelors as they deal with angry gangsters, suspicious cops, and the overwhelming responsibility of fatherhood.