British diamond smugglers use the radiowoman (Phyllis Kirk) from a freighter docked on the Thames to unwittingly "mule" their swag, hidden in cigarettes, past customs, not knowing that she has befriended an Inspector for the Thames River Patrol.
Cinematography
Misty Thames location work elevates the cheap sets beautifully.
Acting
Phyllis Kirk's wary intelligence outclasses the material.

Director
Guy Green
Trivia, insights & behind the scenes
Guy Green won an Oscar for cinematography on 'Great Expectations' (1946) before directing this; his visual polish on a shoestring is the whole appeal.
Phyllis Kirk was American—her 'British' accent here is part of a weird 1950s trend where US actors played UK roles to secure co-production funding.