Barnabas Collins and Quentin's Demon — Marilyn Ross

When Quentin Collins invited Laura Balfour to Collinwood, they knew each other only from the correspondence that had grown out of Quentin's adminition for the haunting waltz her father had composed. Soon Quentin professes to love Laura--but is his love really a threat? His first wife's throat was torn out by a wolflike creature who escaped capture. Since then, other young women have died in the same grisly fashion... in the full of the moon, when Quentin's mysterious "attacks" occur.