Two men go into business supplying medical colleges with cadavers by robbing graves.

A Scotland Yard Detective (Peter Cushing) must investigate a series of murders perpetrated by a giant blood-sucking moth that can take human form.

When his brother disappears, Robert Manning pays a visit to the remote country house he was last heard from. While his host is outwardly welcoming – and his niece more demonstrably so – Manning detects a feeling of menace in the air with the legend of Lavinia Morley, Black Witch of Greymarsh, hanging over everything.