 | Susan Strasberg als Penny Appleby |
 | Ronald Lewis als Robert |
 | Ann Todd als Jane Appleby |
 | Christopher Lee als Doctor Pierre Gerrard |
 | John Serret als Inspector Legrand |
 | Leonard Sachs als Mr. Spratt |
 | Anne Blake als Marie the Maid |
 | Fred Johnson als Father |
 | Madame Lobegue als Swiss Air Hostess (uncredited) |
 | Bernard Browne als Gendarme (uncredited) |
| Frederick Rawlings als Plainclothes Sergeant (uncredited) |
| Richard Klee als Plainclothes Sergeant (uncredited) |
 | Brian Jackson als Plainclothes Officer (uncredited) |
 | Heinz Bernard als Plainclothes Officer (uncredited) |
| Frederick Schrecker als Plainclothes Officer (uncredited) |
| Gordon Sterne als Policeman (uncredited) |
 | Rodney Burke als Policeman (uncredited) |
| Bernard Robinson | Production Design |
| Eric Boyd-Perkins | Editor |
| Douglas Slocombe | Director of Photography |
| Michael Carreras | Executive Producer |
| Clifton Parker | Original Music Composer |
| Jimmy Sangster | Producer |
| Seth Holt | Director |
| Jimmy Sangster | Writer |
| Desmond Davis | Camera Operator |
| John Jordan | Underwater Camera |
| Harry Oakes | Additional Camera |
| Jim Groom | Sound Editor |
| John Crome | Assistant Sound Editor |
| Les Bowie | Special Effects |
| Ian Scoones | Special Effects Assistant |
| Teddy Mason | Sound Recordist |
| George Higgins | Still Photographer |
| James Needs | Supervising Editor |
| John Hollingsworth | Music Supervisor |
| William Hill | Production Manager |
| Bill Constable | Assistant Art Director |
| Len Harris | Additional Camera |
| Egil S. Woxholt | Underwater Camera |
| Terry Lens | Second Assistant Director |
| Stuart Lyons | Casting |
| Thomas Goswell | Art Direction |
| David Tomblin | Assistant Director |
| Dora Lloyd | Wardrobe Master |
| John Crome | Assistant Editor |
| Len Shilton | Sound Recordist |
| Pamela Mann | Continuity |
| Ray Andrew | Clapper Loader |
| Eileen Bates | Hairstylist |
| Basil Newall | Makeup Artist |
| Les Hammond | Sound Recordist |
