Determined to live down his family's reputation, Dr. Frederick Frankenstein (Wilder) insists on pronouncing his name "Fronckensteen" and denies interest in replicating his grandfather's experiments. But when he is lured by Frau Blucher (Leachman) to discover the tantalizingly titled journal "How I Did It" in his grandfather's castle, he cannot resist. With the help of voluptuous Inga (Garr), wall-eyed assistant Igor (Feldman), and a purloined brain, Frankenstein creates his monster (Boyle). Igor, however, stole the wrong brain, and the monster tears off into the countryside, encountering a little girl and a blind hermit (Hackman). Frankenstein finds the monster and trains him to do a little "Puttin' On the Ritz" soft-shoe, but the monster escapes again, this time seducing Frankenstein's uptight fiance Elizabeth (Kahn) with his, ahem, sweet mystery. His love life and experiment in shambles, Frankenstein finally finds a way to create the being he had planned.