A disturbed boy kills his father with his farm tractor and his arm is mangled in the process. He's taken to a mental hospital where he's outfitted with a hook to replace his lost hand and, years later, he's eventually released from the asylum. He returns home to find his mother has remarried, which sets him off on a murderous rampage.

On the way to Rome, a thief captures the Duke of Riviera y Fuentes and decides to take advantage of the opportunity to impersonate him. The thief makes his way to Rome in the duke’s place and seduces the mysterious Lucrecia Borgia who always wears a mask. He’s in for an erotic time at Lucrecia’s palace.