Wartime thriller with film noir elements based on a true story as written in A.P. Scotland's autobiography "The London Cage". The plot has greatly exaggerated the actual events of A.P. Scotland's experiences, including the addition of a fictional love interest.
Jack Hawkins wasn't always renowned for the subtlety of his performances, but he does manage that well here. In this quite plausible adaptation of AP Scotland's fact-based book, he portrays a German officer who works his way up the ranks, ultimately to reach staff rank in the Nazi army - whilst passing on secrets to the British for almost 30 years. The direction is suspenseful and it maintains the tension well - especially towards the end. This is rarely seen, nowadays, but is eminently watchable.