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.
Bernard Lee
Henry Houghton
William Sylvester
Gordon Lonsdale
Margaret Tyzack
Elizabeth Gee
David Kossoff
Peter Kroger
Nancy Nevinson
Helen Kroger
Thorley Walters
Cmdr. Winters
Gillian Lewis
Marjorie Shaw
Newton Blick
P.O. Meadows
