The film is based on the actual events of the Portland Spy Ring trial in the U.K. A disgruntled Navy Clerk is transferred to a secret research establishment and is subsequently black-mailed/paid by Czech intelligence to procure secrets for them. He seduces the secretary who controls the most secret documents, and they enjoy the fruits of their treachery until the British authorities begin to close in on them.
| Production | Leslie Gilliat | Producer |
| Writing | Frank Launder | Writer |
| Directing | Robert Tronson | Director |
| Editing | Thelma Connell | Editor |
| Writing | Peter Barnes | Writer |
| Camera | Arthur Lavis | Director of Photography |
| Costume & Make-Up | Ernest Gasser | Makeup Artist |
| Production | Paul Sheridan | Casting |
| Crew | Cecil Mason | Sound Recordist |
| Camera | Jack Lowin | Camera Operator |
| Art | Norman G. Arnold | Art Direction |
| Costume & Make-Up | Daphne Vollmer | Hairdresser |
| Directing | Derek Cracknell | Assistant Director |
