British mathematician Sebastian (Sir Dirk Bogarde), working on code decryption, unexpectedly falls in love with decrypter Rebecca Howard (Susannah York). This leads them to a complicated intrigue within the codebreakers.
Sebastian
During the Cold War, the chief of a British intelligence code-breaking section falls in love with a new employee and shields an old co-worker, accused of Communist affiliations, from the wrath of the security branch.