a young james mason do a fine job in this film . the story be set a few year before the start of ww ii . mason be a guest at a quiet resort hotel in france . his camera be accidentally use by a german spy who have an identical one . when mason take a roll of film to be develop and the roll contain several picture of top secret french aircraft and facility . the police question mason and be able to determine that he be innocent in the matter . but and they use the charge against him a leverage to get him to assist them in find out which of the other hotel guest be the spy . how he succeed make for a most interesting and tension fill story .