James Mason as Cmdr. Max Easton

George Sanders as Sir Charles Holland

Vera Miles as Virginia Killain

Robert Flemyng as Cmdr. John Larkin

Oliver Johnston as Minister

William Kendall as Tom

Duncan Lamont as 1st Special Branch man Gregson

Harry Andrews as Capt. Graham

Peter Barkworth as Sub Lt. Brown

Rachel Gurney as Clara Holland

Martin Stephens as John Holland

Waveney Lee as Marcia Holland

Charles Carson as Robert Holland

Junia Crawford as Susan

Henry B. Longhurst as Club Member (as Henry Longhurst)

Roger Maxwell as Club Member

Gerald Case as Club Member

Donald Bisset as Club Member

Desmond Roberts as Club Member

Reginald Smith as Club Steward

Rosemary Dorken as WREN Officer

MacDonald Parke as Jason Parrish (as Macdonald Parke)

Mavis Villiers as Adele Parrish

Ernest Clark as Cmdr. Bates

Alexander Archdale as Local Doctor (uncredited)

Basil Dignam as Lt. Cmdr. Evans at P.R.O. (uncredited)

Mabel Etherington as Nightclub Patron (uncredited)

Gordon Harris as 2nd Special Branch Man Jones (uncredited)

Barbara Hicks as Miss Price (uncredited)

John Horsley as 1st Editor (uncredited)

Frederick Kelsey as Club Member (uncredited)

John Le Mesurier as Head of the Admiralty (uncredited)

Ronald Leigh-Hunt as 2nd Editor (uncredited)

Richard Marner as Russian Officer Cornered by Max Easton (uncredited)

William Mervyn as Capt. Balfour (uncredited)

Andre Mikhelson as 2nd Russian Officer (uncredited)

John More as American General at Embassy Party (uncredited)

Dickie Owen as 2nd Policeman (uncredited)

Frederick Piper as Hall Porter (uncredited)

Pat Ryan as Nightclub Patron (uncredited)

Stanley Zevic as 1st Russian Officer (uncredited)