There are secrets being leaked and Patrick Allen is told to find out who and how, with American James Maxwell seconded for US interests.
It's a slow and deliberate movie, far from the slam-bang and sexcapades of the James Bond franchise. Allen is still in love with ex-wife Zena Walker, and she with him, but their marriage could not take the strain. Maxwell is interested in Jacqueline Ellis, but though she makes a lovely dinner companion, the work they do is too dirty for her to ever think of marriage. In between these reliefs, such as they are, from the main story, they track the route of the stolen secrets to a doctor's office, and set up in a betting shop across the street to surveil.... and run into problems when a successful bettor puts the shop in the red.
It's unglamorous and even occasionally dull to watch their progress, up until the slam-bang ending. The result is a film that is too realistic to be very entertaining, but stands as a useful correction to the usual image of spywork.