8-year-old Jesús has been living in a crumbling underground facility since he was born with eight survivors of an apocalyptic war: the leader Maria and her lover Pablo, gays Lucas and Mateo, astronomer Magdalena, teenager Ana, soldier Pedro, and lonely Judas. They are permanently under surveillance, threatened by the contaminated mutants The Strangers, and once a day they have to lock themselves in their rooms without heating to protect against the dangerous ghosts The Invisibles that attack in the Cold Hour. They cannot go to the surface, destroyed by a nuclear war. When they need supplies, medications, and ammunition, they organize expeditions to a store. When the menace of The Invisibles affects the safety of the group of survivors, they need to reach the surface.