Laughton hams it up as the evil Alan de Maletroit (Laughton), who's imprisoned his brother Edmond (Cavanagh) for the crime of marrying Alan's one love. Now Maletroit wants to destroy his niece Blanche (Forrest) as well. But Edmond's faithful retainer Voltan (Karloff) is determined to stop the evil. Low-budget hokum adapted from the Robert Louis Stevenson story "The Sire de Maletroits's Door."