James Mason is on vacation at a French hotel shortly before World War II begins. While retrieving some photographs he’s had developed, he finds himself arrested by the police, who suspect him of taking unauthorized pictures of areas near Toulon that could be valuable to those opposing the government. Although the officer in charge seems inclined to believe his story, Mason is nonetheless compelled to remain at the hotel under observation, with the threat of imprisonment, exile, or even involvement with the Gestapo hanging over him. The hotel is full of people who might be suspicious – including Lucie Mannheim, Raymond Lovell, and Herbert Lom – and he’s tasked with identifying the would-be traitor without becoming entangled in a complex scheme. Mason gives a good performance, as do Lom and Frederick Valk, and the film feels akin to a round of Cluedo; there are numerous hints and possible culprits, and for the most part, it maintains a reasonable level of tension until the villain is revealed, after which the ending falls rather disappointingly short. It’s still enjoyable enough to recommend, however.

Source on TMDB