James Mason as Ulysses Diello

Danielle Darrieux as Condesa Anna Staviska

Michael Rennie as Colin Travers

Walter Hampden as Sir Frederic Taylor

Oskar Karlweis as L. C. Moyzisch

Herbert Berghof as Col. von Richter

John Wengraf as Count Franz Von Papen

Ben Astar as Siebert

Roger Plowden as Keith Macfadden

Diane Adrian as Singer on French Record (voice)

Patrick Whyte as Code Clerk

Hanna Axmann-Rezzori as

David Bauer as

Lawrence Dobkin as

Martín Garralaga as

Lumsden Hare as

Richard Loo as

Lester Matthews as

Keith McConnell as

Frank McLure as

Charles Meakin as

Alberto Morin as

Nestor Paiva as

Michael Pate as

Konstantin Shayne as

Ivan Triesault as

Otto Waldis as

Alfred Zeisler as

Stuart Hall as British Military Attaché (uncredited)