cat and mouse (1958)

aka The Desperate Men.
The film opens with Ann meeting with a blackmailer, who claims to have worked with her father, a diamond thief. He is after some diamonds that were never recovered following a robbery and thinks she knows where they are. In a struggle Ann knocks out the blackmailer and is startled when American Rod Fenner enters the room at just this point. She faints and when she comes to Rod convinces her that she has killed the blackmailer. The two end up on the run from the police, but is Rod on the level and did Ann really kill the blackmailer?
The atmosphere builds slowly, uping the tension and the claustrophobia. A small scale but entertaining film, with some nice details in the street scenes, giving a real sense of the period.