Román, a member of a terrorist group, has to place one of the four bombs on the train going west. At the same station, and at the same time of the attack, Verónica, a single mother, goes to meet her son Javi to take him to school. Román and Verónica live in the same building, but they have never seen each other. Fate intervenes when, on the way to the station, they meet in the elevator.