American and British police join forces to track down a group of criminals who are manufacturing artificial diamonds.

Unjustly neglected little noir, as well as Britain's first 3-D film (though released flat). Long considered lost, but much deserving to be more well known. Much of it is fairly typical police procedural stuff, but a sequence on the escalator of St. John Wood Station is a wonderfully well done piece of filmmaking, and the explosive ending nicely anticipates Kiss Me Deadly, released the next year. Highly recommended.

Note: O'Keefe is supposedly credited as director n US prints, and Tully on UK prints (union rules), but the copy I watched had the UK title, but credited O'Keefe as director. So who knows what went on!