Joe Dennison

Dennis O'Keefe

Marline Miller

Margaret Sheridan

Insp. McClaren

Philip Friend

Thompson Blake

Alan Wheatley

Yeo

Francis de Wolff

Hunzinger

Eric Berry

Sgt. Smith (as Ann Gudrun)

Gudrun Ure

Hoxie

Michael Balfour

Sgt. Smith

Ann Gudrun

Lascelles

Seymour Green

Dr. Eric Miller

Paul Hardtmuth

Castle

Cyril Chamberlain

Sir Stafford Beach

Colin Tapley

Commander Gillies

Donald Gray

Mickey Sweeney (uncredited)

Paul Carpenter

Mr. Pritchard (uncredited)

Hugh Morton

Dr. Cully (uncredited)

Alastair Hunter

Mr. Hawkins (uncredited)

Gordon McLeod

Ballistics technician (uncredited)

Paul Whitsun-Jones

Police informer (uncredited)

Larry Burns

Diamond laboratory technician (uncredited)

Don Cunningham

Sam (uncredited)

Victor Wood