Dark Intruder (1965)

The story takes place in 1890 San Francisco, where a series of gruesome murders attracts the attention of Brett Kingsford (Leslie Nielsen), a playboy detective with a secret crime lab, a library of occult tomes, and an invaluable dwarf assistant (Charles Bolender). His friend, Robert (Mark Richman), soon to be married to Evelyn (Judi Meredith), keeps having trance-outs at the oddest times, and looks to be a likely suspect - especially since he knows the victims. However, the killer growls like a beast and kills with a set of murderous bestial claws, two attributes which Robert lacks.