Once in London, the workaholic Hull is visited by an Oriental colleague (Oland) who asks for the flower to help patients, or so he claims. Oland, who carries a charmingly sinister persona, hints that he was the werewolf Hull fought off in Tibet. Meanwhile, Hull's Dr. Glendon, much to his surprise and horror, become a werewolf. The transformation leaves him evil, and he kills several women when the moon is full. An old beau (Matthews) of Glendon's neglected wife Lisa (Hobson), visits the community and begins to suspect Hull.
Notes: The film seems to have originally been envisioned as a vehicle for Boris Karloff and Bela Lugosi in the Hull, Oland roles.