This is quite possibly the best of the Hammer films, it's labeled as 'horror', but is more of a classic psychological thriller. The plot revolves around Susan Strasberg's visit to her father's estate after a decade of estrangement. Her physical condition (in a wheelchair, unable to walk after a horseback riding accident) and the recent death of her long time companion set her up to be the 'perfect victim'.
Her step mother, Ann Todd, and the family chauffeur Ronald Lewis are oh-so accommodating and thoughtful, explaining that her father is out of town. But, Strasberg starts to see dead dad popping up all over, while Todd, Lewis, and family doctor Christopher Lee try to persuade her she's just stressed and overly-imaginative. Is she crazy? Are they gas-lighting her? Although the viewer will remain suspicious, we are wisely kept in the dark as to motives (of all the characters..) until the final twist. The black and white photography is really well done -moody, shadowy - and is probably as important as the characters which is not the usual Hammer screamer in intense shades of red.