In Spain, the sports journalist Juan has a perfect life with his wife Sonia: they have just had a baby and moved to an old house that needs to be repaired in a fancy neighborhood. When Juan's sister and her husband visit the couple, they give them an electronic nanny to monitor the baby's room. During the night, Juan and Sonia hear voices in the room but they do not find anybody. On the next day, Juan hires an alarm system for the house and a monitor to observe the baby's room. When Juan sees a man in the room, he gets a knife to protect his son. However, Sonia believes her husband is insane and moves to her mother's house. Juan investigates the happening with the former journalist Domingo, who explains him the paradoxical experiment Schrodinger's Cat and the existence of parallel worlds. Further, he advises the obsessed Juan to leave the house otherwise could be trapped in another world.