A werewolf prowls around at night but only kills certain members of one family. It seems like just a coincidence but the investigating Inspector soon finds out that this tradition has gone on for generations and tries to find a link between the werewolf and the family, leading to a frightening conclusion.
Alex, the nice big dog we meet, is not harmed. We learn about the death of a spaniel, and it is mentioned in detail a number of times, but occurs off screen.