Just saw this on Talking Pictures channel (UK, old films and TV), and the critical reviews on here are rather unfair. Bear in mind what this was, a B feature, just over an hour long, and a small budget!
It tells a perfectly reasonable little story, though the time confines don't allow many choices for the actual villain?! The plot is worked out quite well, and you need to make allowances for how things were in the early 50s, but that shouldn't be so tricky.
One glaring plot error (?) has been mentioned, re taking a flash photo through a window, but then for decades we've seen press snappers taking an attempted pic through the windows of vans taking prisoners to and from courts -- don't they know better too??!!
And it was nice to see Blackman & Jackson taking their next steps up the acting ladder.