Rachel, a nineteen-year-old student, regularly babysits for Stéphane Mancini, a forty-year-old business executive who lives alone with Hugo, his two-year-old son. Stéphane often goes out at night and doesn't return until early morning. Rachel sometimes makes the most of this to invite Christine, one of her friends, over. One evening, while Hugo is asleep, the two friends keep themselves entertained by exploring the apartment, trying on Stéphane's ex-wife's clothes, and rummaging through the bathroom cupboards. Boris and Steve – their boyfriends – join them and very soon the evening turns into an impromptu party. Stéphane suddenly returns home, earlier than expected. He kicks everyone out – everyone that is, except Rachel, who is still wearing an outfit belonging to his ex-wife.