A beautiful summer afternoon. An invitation to a birthday party gone wrong. A woman in black. A disturbing nurse. Why these deaths?

Paris by night. Alex, 22, wants to become a filmmaker. He is fascinated by first times and his girlfriend, Florence, has just left him for his best friend, Thomas. First break-up, first attempted murder: Alex tries to strangle Thomas, but gives up and wanders the streets. That evening, Mireille, a girl from provincial France who has come up to Paris to make commercials, is left by her boyfriend. Alex witnesses this separation. These two tormented souls run into each other at a party.