Son of Frankenstein stars Rathbone as Baron Wolf von Frankenstein who, with his wife Elsa (Josephine Hutchinson) and son Peter (Donnie Dunagan), returns to his late father's estate. Near the castle lives Ygor (Bela Lugosi), a crazed blacksmith whose neck was broken in an unsuccessful hanging attempt
Among the castle's remains, Frankenstein discovers the remains of the Monster (Boris Karloff) and decides to try to save his family name by resurrecting the creature to prove his father was correct. He finds, however, the Monster only responds to Ygor's commands
The film was originally announced in August 1938 after a successful theatrical reissue of Dracula and Frankenstein
Son of Frankenstein was initially announced under the title After Frankenstein