A mental patient detained in a psychiatric hospital escapes from confinement and is dedicated to roam the outskirts of Madrid. His mind is no more disturbed rationale to kill. After murdering two girls on the banks of a river, go stringing a series of murders each more repulsive, spreading terror in the place. José and Antonio, two good friends, prepare a fun weekend at the country house that Joseph's family owns on the outskirts of the city. Taking this opportunity to invite two beautiful sisters, Anne and Laura, who accept the invitation. Ana, the eldest, works as a secretary, unhurried lives and loves Antonio. Laura on the other hand, has a shy and introverted character that has intensified after a recent failed love affair. Everything seems it will be a fun weekend for two couples.