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.
Det. Insp. Dan Barker
Judy Roberts
Det. Sgt. Mack McLeod
Charlie Williamson
Albert Fisher, called both "Al" and "Bert"
Steward Alfred Gordon, also called "Al"
Paddy Maclure
John Hendrick
Ship's Captain Watford
Customs Chief J. S. Blake
Adams
