The Mad Monster is a 1942 mad scientist/werewolf movie. It has a convoluted plot centered on the mad scientist's revenge against the scientists who rejected him. It stars George Zucco (House of Frankenstein 1944), Johnny Downs (Babes in Toyland 1934) and Reginald Barlow (Horse Feathers, uncredited parts in King Kong, Captain Blood and Great Expectations, Bride of Frankenstein, Little Lord Fauntleroy, The Man in the Iron Mask).
I found this one moved slowly. Even tediously. I got a bit tired of him talking to himself, filling us in on all the background information.