Early Hitchcock curiosity, an adaptation of a stage detective story which for two thirds of its short running time is filmed like an old dark house horror, full of expressionist shadows and close ups of threatening hands. Then the last third is a chase, utilising models of modes of transport, none of them convincing.
The McGuffin of the search for some stolen jewels is banal, and Hitch gives us little to divert us from that weakness. The cast is unremarkable. Hitch doesn't tell its confusing story that well. There is some decent humour and a plenty of eccentricity.
What is different from earlier films, is there is a lot of physical action in the last third, much of it well realised. There are characters holding on to the outside a speeding train. Over the years we would see many Hitchcock heroes and villains clinging on over a precipice or some other hazard.
Hitch didn't want to make Number Seventeen and his relationship with British International Pictures was falling apart. This was his last production for them. The complicated story is a bit of a muddle, but if you manage to follow it, then there's just about enough of the Master here to make this reasonable entertainment.