Heiress Betty Ward is worried about her twin sister, who has eloped with Jeremy Frene. She follows them from Paris to the Frene estate at Collinwood -- but arrives too late! Her twin is dead, victim of a mysterious illness. Her body has been sealed in a crystal coffin and kept in a darkened room. Jeremy swears that because her ghost returns to the castle each night, he refuses to bury the coffin. Betty is convinced her sister's death was not a natural one. Jeremy's aunt opposed the marriage. Her ally against the couple seems to have been Quentin Collins a suspected werewolf.