Firstly, Miki Hood - what a beautiful young lady! I wonder why she never made it big because she's absolutely lovely. She looks like a Disney princess who could be another sister of Loretta Young.
This film is based on a long running popular radio show, with professional cockney Gordon Harker as the personable sleuth. With a long track record of good scriptwriting, the story used for this is intelligent and intriguing. Eugene Forde - never heard of him - directs this adequately and ensures the tension ramps up at a good pace.
Like another other forgotten detective series: Philo Vance, it's the plot rather than the characters which the Horleigh stories rely on. Harker does however give his grumpy old copper a bit of personality which makes this a hundred times better and engaging than the tiresome Vance movies. It's hardly Hitchcock or Holmes, Poirot or even THIN MAN but although it's not super-original, it is professionally made, well acted and well written.