Seriously ill, concert pianist Karen Duncan is admitted to a Swiss sanitorium. Despite being attracted to Dr Tony Stanton she ignores his warnings of possibly fatal consequences unless she rests completely. Rather, she opts for a livelier time in Monte Carlo with dashing Paul Clermont.

In this sequel to the original story, Monte Cristo count Edmund Dantes (Martin Kosleck) returns to Paris to get revenge but soon finds himself pursued by a cruel policeman. The count's brave wife Haydée throws the cop off her husband's scent by dressing up as the masked avenger herself and proving that she too is most competent with a sword.

When author Charles Regnier returns to Paris with a best-selling book that criticizes the government, he's tormented by frequent blackouts. After a mysterious cat-like creature slaughters people close to him, Charles is suspected of murder. Charles fears that he is the beast, but his paramour Marie and best friend Henry, believe he's innocent... until the creature begins to stalk Marie.