Dr. Gustav Niemann escapes from prison along with his hunchbacked assistant Daniel, for whom he promises to create a new, beautiful body. The two murder Professor Bruno Lampini, a traveling showman, and take over his horror exhibit.
Niemann and Daniel move on to the flooded ruins of Castle Frankenstein in Visaria, where they find the bodies of Frankenstein's Monster and Lawrence Talbot, the Wolf Man, preserved in the frozen castle. Niemann thaws them and promises to find Talbot a cure for the curse. Niemann is more interested in reviving the monster and exacting revenge on two traitorous former associates than in keeping his promises. Talbot transforms into a werewolf and kills a man, sending the villagers into a panic. Niemann and Daniel save a gypsy girl named Ilonka, and Daniel falls in love with her; it is unrequited, however, as Ilonka falls in love with Talbot.
Daniel is killed when he's thrown out of a window by Frankenstein's Monster.