This film essentially begins with an American agent working for the Office of Strategic Services (OSS) by the name of "Hubert Bonisseur de La Bath" (Kerwin Mathews) being sent to Corsica to investigate the disappearance of another agent named "William Roos" (Jacques Harden) who had been investigating the presence of a secret Soviet submarine listening device in that area. Naturally, since he has very little information to go on the first person he seeks out is a man by the name of "Renotte" (Henri-Jacques Huet) who was the last person to see William Roos alive. However, sensing that Renotte isn't telling him the full truth he then turns his attention to his beautiful assistant "Brigitta" (Nadia Sanders) who seems much more open and honest. What he doesn't know, however, is that his presence has been monitored from the very start and there are certain people who will do whatever it takes to prevent him from discovering their clandestine operation. Now rather than reveal any more I will just say that this film turned out to be a pretty good Eurospy movie in that it had an intricate plot and some good action scenes here and there to keep things interesting. Likewise, having a couple of beautiful actress like Irina Demick (as the Soviet agent "Lucia") along with the aforementioned Nadia Sanders certainly didn't hurt either. In any case, although some might not like the fact that it was filmed in French (with English subtitles) and produced in black and white, I enjoyed this film and have rated it accordingly. Slightly above average.