Javier Muñoz was a successful advertising executive, but after a year of unemployment, he and his family are forced to leave the apartment they can no longer afford. One day, Javier discovers that he still has a spare set of keys to his old house and begins to spy on the young couple now living there. Gradually, Javier starts to infiltrate the lives of the new homeowners, determined to try to regain the life he has lost... at any cost.