 When the British high command get wind of a German plan, titled The W Plan, from the lips of a dying German officer, Major Ulrich Muller (George Merritt), they send Grant behind enemy lines to learn the details.After successfully being dropped by airplane near the German town of Essen, where he makes his way to home of the dead German who was responsible for the plan.Grant is chosen because he speaks fluent German, having spent a significant amount of time in Germany prior to outbreak of hostilities.