a modest but quite competently do spy thriller set in 1939 france . the plot line be strongly reminiscent of 1930s british drawing room detective thriller you expect hercule poirot to reveal himself at any moment . james mason be an austrian refugee from the nazi who be accuse of spy and then use a a decoy by the french authority to flush out the real spy and who turn out to be herbert lom play his usual sinister baddie . mason and lom turn in their usual workmanlike performance and give the whole thing credibility and wind up to a rouse finale in the best hitchcock tradition .