Comfortably-off and terribly in love, Rebecca and Romain desperately want a baby, but without success. Rebecca suffers from nightmares and dreads the arrival of Mickaël, Romain's unstable brother, who's moving in opposite. When Mickaël announces his future fatherhood, tension rises. He hits Émilie, his partner. The next day, she disappears.

Louise is 8. When she's attacked by a particularly violent pupil, Mickaël, the boy's brother, Romain, comes to her defence. It's the start of a great friendship. One day, Louise misses the bus. As her parents try to catch up with it by car, she spots Mickaël, breezeblock in hand.

Four years after Mickaël's death, Romain still remains vulnerable. He and Rebecca now have a little girl, Emma. One day, when their daughter is hospitalised, Romain discovers that their blood groups are incompatible. He begins to wonder - is he really Emma's father?