The Undying Monster

The Undying Monster is a 1942 horror and mystery film, also known as The Hammond Mystery, featuring a werewolf as the primary antagonist. The movie, directed by John Brahm, is based on the 1922 novel by Jessie Douglas Kerruish.

Curtis investigation at the Hammond household reveals a number of unusual circumstances, including slamming doors and clanking chains, a recently entered secret room supposedly locked for years, and a statue of a strange doglike creature in the Hammond family crypt. During his investigation, one of the initial victims of the attack dies after being in a coma, and the case is sent to an English jury for judgement. Upon hearing testimony from members of the Hammond family and their associates, the jury rules that the victim died at the hand of an unknown person or creature of unknown species.After the ruling, Curtis looks for evidence upon the victims body. He finds a hair that he later identifies as a wolfs, but the hair disappears mysteriously soon after he analyzes it. The monster attacks again, this time kidnapping Helga Hammond Heather Angel, but Curtis and the police chase him down. When shot, the monster transforms into a human being, and we discover that it is actually Oliver Hammond. Afterwards, Dr. Jeff Colbert Bramwell Fletcher, a friend of the Hammonds, reveals that they have been afflicted with lycanthropy for generations that is, they are werewolves and he had been attempting to cure them of the disease. ........

Source: Wikipedia