Trailer for Demons of the Mind, the 1974 classic starring Paul Jones, Patrick Magee and Yvonne Mitchell.
Count Zorn, a wealthy widower, locks up Emil and Elisabeth, his two young adult offspring, afraid that they will go mad, as did his wife. He then invites Falkenberg, a doctor of dubious reputation, to supervise the young people’s mental health. Meanwhile, in the vicinity of their mansion, grisly murders are happening.