Mac discovers that Joan's rich American husband Jason ( Robert Hutton ) is carrying on with the pretty Diane. Jason tells Mac to stay out of his business, but of course our hero is not going to let an ex-girlfriend go insane.
Joan thinks the answer may lay in her past...
Written by Roger Parkes ( who also contributed to 'The Prisoner' and later, 'Strange Report', 'Survivors', and 'Blake's Seven' ),this is the stuff of Victorian melodrama - poor woman been driven off her trolley by greedy relative - but it is well done and director Freddie Francis pulls off some stylish scenes, most notably when Joan visits her father's grave. Some of the shots of Joan's home look as though there was heavy fog around when they were filming. It contributes no end to the suspenseful atmosphere. The problem with the story is that there is no real mystery here - it is obvious Robert Hutton is the baddie.
Francis worked with Hutton on the films 'Torture Garden' and 'They Came From Beyond Space' ( 'a pity they ever made the journey' said one critic of the latter ) in 1967, which also starred another Francis' favourite - Jennifer Jayne.
Philip Madoc plays a psychiatrist, and a creepy one at that.
Joan's mother, Mrs.Caggan, had helped her murder her father years earlier, and has been stalking her daughter, rather than directly confronting her. When Jason stands revealed as the dog killer, he and Mac have a fight that ends with Jason crashing into a mirror. Seven years bad luck for him then.