Mona lives with her adult son, Joël, who is "slow," as they say. He works in a specialized facility and is passionately in love with his coworker, Océane, who is also disabled. While Mona knows nothing of their relationship, she eventually learns that Océane is pregnant, and the symbiotic bond between mother and son falters.

Marco, who is in his twenties and a bit lost, helps out a friend by standing in for him at his place of work: an emergency center for lifts. At around 3 am, a young woman called him: trapped in a broken-down car, she was having an anxiety attack. Marco tried to reassure her on the phone, but as no technician was available to help, he decided to go and rescue her himself. Unfortunately, when he arrives, the young woman has vanished into thin air. And so begins his incredible quest to track down this enigmatic stranger in Paris on the night of Valentine's Day.