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.
John Bentley
Det. Insp. Dan Barker
Phyllis Kirk
Judy Roberts
Leonard White
Det. Sgt. Mack McLeod
Glyn Houston
Charlie Williamson
Patrick Jordan
Albert Fisher, called both "Al" and "Bert"
Harold Ayer
Steward Alfred Gordon, also called "Al"
David Hurst
Paddy Maclure
Charles Lloyd Pack
John Hendrick
