Dementia 13

Produced by Roger Corman, and evidently made under his presiding spirit, this runs briskly through one of those family reunion plots in which the challenge is to guess which seemingly benign member of the family is the mad axe-murderer who's steadily picking off the rest. The location (an Irish castle) is used imaginatively, the Gothic atmosphere is suitably potent, and there's a wonderfully sharp cameo from Patrick Magee as the family doctor.