The Incredible Theft

Lord Mayfield, an aircraft manufacturer, invites Lady Vanderlyn (who is suspected of being a spy for the Germans) to his country house, and he has a plan to trap her. But when Lady Mayfield hears about her husband's plan, she sends for Poirot. Lord Mayfield's plan all seems to go horribly wrong, and Poirot has to tell a few home truths.