Sir Robert Cargrave (Ronald Lewis), a gifted London doctor researching experimental treatments for paralysis, receives a mysterious letter written in a familiar hand. Following its instructions, Cargrave travels to the foggy mountains of Gorslava, where he must treat the horribly disfigured Baron Sardonicus (Guy Rolfe). Sardonicus has married Cargrave's childhood sweetheart, Maude (Audrey Dalton), and threatens to harm her should the good doctor fail to cure him of his bizarre affliction.