Cedric Hardwicke, Ralph Bellamy, Lionel Atwill, Bela Lugosi, Evelyn Ankers, Lon Chaney Jr., Janet Ann Gallow, Barton Yarborough, Doris Lloyd, Leyland Hodgson, Olaf Hytten, Holmes Herbert, Richard Alexander, Lionel Belmore, Chet Brandenburg
Frankenstein's unscrupulous colleague, Dr. Bohmer, plans to transplant Ygor's brain so he can rule the world using the monster's body, but the plan goes sour when he turns malevolent and goes on a rampage.
Your father was Frankenstein. Your mother was lightning. Of course the problem with the Frankenstein sequels, of the Universal Studios kind, was that they had to follow the genre firework that was "Frankenstein (1931)" and the monolithic titan that followed that one in 1935, "The Bride of Frankenstein". These are tough acts to follow - still are actually! "Son of Frankenstein (1939)" managed...