| Cast list | | Tony Britton | as | Dr. Robert Marriott | | Virginia Maskell | as | Dr. Lucy Byrne | | Ian Bannen | as | Alan Andrews | | Kenneth Griffith | as | Dr Shole | | Peter Cushing | as | Professor Sewell | | Thorley Walters | as | Special Agent Prince | | Donald Pleasence | as | Parsons, alias Bill Brown | | Spike Milligan | as | Arthur, lab orderly | | Raymond Huntley | as | Sir George Gatting the Minister of Defense | | Sam Kydd | as | Slater | | Anthony Booth | as | Parkin | | Basil Dignam | as | Dr Childs | | Brian Oulton | as | Director | | Robert Bruce | as | Levers | | John Payne | as | Iverson |
| | Crew list: | | John Boulting (Director) | | Roy Boulting (Director) | | Nigel Balchin (Writer) |
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