Set in Rome during the 1880s, wealthy and tyrannical patriarch Gregorio Ferramonti (Anthony Quinn) abruptly closes his family business and cuts off his three adult children—Pippo (Gigi Proietti), Mario (Fabio Testi), and Teta (Adriana Asti)—leaving them to fend for themselves. Into this dysfunctional dynamic steps Irene (Dominique Sanda), a calculating woman who marries the weak-willed Pippo. Driven by ambition to secure the vast Ferramonti fortune, Irene systematically manipulates the men of the family. She begins a passionate, secret affair with her brother-in-law Mario while simultaneously seducing the aging Gregorio himself. By becoming the elderly patriarch's mistress and sole confidante, Irene maneuvers Gregorio into changing his will entirely in her favor before his death, triggering a fatal wave of betrayal and tragedy among the siblings.