High tension, low budget thriller which is among the best British B films ever made. This is due to a much better cast than is usual for this kind of production, but mainly because of Lance Comfort's direction which wrings all of the suspense out of the inspired premise.
A maladjusted misfit (Robert Shaw) abducts the son of a wealthy banker and locks him in an isolated house with a bomb stitched into a doll timed to explode at the hour of the title. Then the kidnapper walks into the parents' swanky mansion and demands a huge ransom.
A paunchy John Gregson investigates but his task is complicated when the angry father (Alec Clunes) kills the criminal. And the clock still ticks. Some of the thoughtful dialogue is just editorialising on related themes, but this is interesting. Maybe the breaking of the case is a little humdrum, but we get a nice ironic twist at the rousing climax.
There's an expressionist look to the opening scene while the kidnapper sews up the the doll, though such visual flair is rationed. The budget won't allow many stylistic flourishes, but the plot is well designed and assembled. It's a short, lean, exciting thriller with a psychological edge and no lulls. Hitchcock on a budget.