A modest but quite competently done spy-thriller set in 1939 France. The plot-line is strongly reminiscent of 1930s British drawing room detective thrillers - you expect Hercule Poirot to reveal himself at any moment. James Mason is an Austrian refugee from the Nazis who is accused of spying and then used as a decoy by the French authorities to flush out the real spy, who turns out to be Herbert Lom playing his usual sinister baddie. Mason and Lom turn in their usual workmanlike performances and give the whole thing credibility, winding up to a rousing finale in the best Hitchcock tradition.