James Mason is having an holiday in an hotel in France just before the outset of WWII. When he goes to collect some developed photographs he has taken, he is detained by the police who accuse him of illegally photographing sites around Toulon that might be of interest to the enemies of the Republic. It's pretty clear that the investigating officer believes his claims of innocence, but he is still sent back to keep tabs on the other guests at the hotel or face prison, deportation and quite possibly the Gestapo. The hotel has no shortage of likely suspects - Lucie Mannheim, Raymond Lovell and…