Trailer
 | Eric Portman as Kuprin |
 | John Gregson as Smith |
 | Marius Goring as Laye-Parker |
 | Martita Hunt as Madame Kuprin |
 | Natasha Parry as Vera |
 | Mervyn Johns as Holloway |
 | John Phillips as Trifonov |
| Noel Johnson as Lowther |
 | Heather Chasen as Isabel |
| Michael Barrington as Rowson |
| James Urquhart as McPherson |
| Wynford Vaughan-Thomas as Radio Commentator (voice) |
 | Edward Burnham as Sir Geraint Lloyd |
| John Ruddock as Professor Ridley |
| Irene Sutcliffe as Miss Probert |
| Pauline Winter as Miss Lipscomb |
| Raymond Farrell as Journalist |
| Alexis Chesnakov as Leonidov |
| Ann Patrick as Nina |
| Alfred Hoffman as Hotel Clerk |
 | John Bennett as Zagornetz |
 | Dorothea Phillips as Madame Lebedev |
| Michael Ivan as Bakaleinikov |
 | Gabriel Toyne as Lebedev |
 | Julia Arnall as Annaliese Kern |
| Gregori Tcherniak as Gypsy Musician |
| Geoffrey Sisley as Gypsy Musician |
 | Tutte Lemkow as Singer |
| Sara Luzita as Gypsy Dancer |
| John Rutland as Liftman |
 | Kenneth J. Warren as Makarov |
