When Don Juan returns home after years of travel, he brings with him a beautiful and mysterious young wife, Dona Pepa. Despite her beauty, Dona Pepa is mistrusted and disliked by everyone.
Several years after this, Don Juan invites his nephew, Don Luis, for an extended visit. Don Luis takes an instant dislike to his aunt. Moreover, he often sees a sinister snake around the house, which fills him with fear and loathing. He soon realises that this snake is Dona Pepa in another form.
He seeks the advice of a hermit who tells him how to deal with the evil woman. But Don Luis is reluctant to take action against his aunt, until something happens that leaves him no choice. A chance meeting with a former servant leads him to discover the strange method by which he can conquer the evil serpent woman.
