On his way to an awards ceremony, Mr. Sebastian (Dirk Bogarde) runs into Becky Howard (Susannah York) on the street, and although they get off to a rough start, he ends up offering her a job when she recognizes his name backwards. It turns out he runs the all-female decoding office of British Intelligence, and she is to be a code-breaker. Once she settles into her new job and starts falling for Sebastian, however, a security breach erupts and puts everything into jeopardy.