Sisters Lígia and Guida live in the same house with their respective husbands, Décio and Paulo. On her wedding night, Lígia discovers that her husband Décio is impotent, leaving her unfulfilled and deeply rejected. Desperate and suicidal over her situation, Lígia prepares to jump off a balcony, but Guida stops her. To save her sister's life and give her sexual release, Guida makes a fateful offer: she lends her own husband, Paulo, to Lígia for one night. However, after the single night, intense passion and obsessive jealousy ignite between Lígia and Paulo, plunging the household into a tragic spiral of betrayal, guilt, and deadly obsession.