Jimmy Sangster's psycho thrillers for Hammer tended to concentrate on young women - Susan Strasberg in Scream of Fear, Jeanette Scott in Paranoiac, etc. This one is about a young man, Robert Webber who wakes up as an amnesiac. His only clues are a torn photo from a newspaper and the fact that a mysterious benefactor is paying for the rent on an apartment.
Webber gives a solid, professional performance but to be honest I didn't really care what happened to him - I get that Sangster was trying to mix things up with a male protagonist but it would have been better with a female: they seem more vulnerable; its easier to believe people thinking they are going insane. Or maybe it could have worked with a guy, just someone more likeable or at least empathetic - Webber's a cold actor, who struggles to convey fear/paranoia in an interesting way.
The storyline rips off tropes from Laura (person they think is dead isn't) Gaslight (being driven insane) and Vertigo (fake dead girl is all part of a scheme to frame someone for murder). And really there isn't enough here for a feature - it's like enough plot for a one hour anthology episode or something. They pad it out with flashbacks to Webber's past.
The snazzy flat in London lacks creepy atmosphere you get in earlier movies in the series. I had heard that director Freddie Francis wasn't really into the project and you can tell - it receives lethargic handling. And this is the sort of movie that badly needs energetic, atmospheric direction.
On the plus side, the acting is strong - as said before, Webber isn't a great star but can act; Jennifer Jayne is winning as the nurse who falls for Webber (she's shamefully under-used in the story, even as a red herring); Mauriece Denham offers authority as a private investigator; Leila Goldoni adds glamour as the Kim Novak figure.