内容简介：
""Wanted: young men to enlist in Uncle Sam's submarine fleet for service in European waters." The magic words stood out in bold type from the newspaper that Jack Hammond held spread out over his knees. Underneath the caption ran a detailed statement setting forth the desire of the United States Government to recruit at once a great force of young Americans to man the undersea ships that were to be sent abroad for service against Germany. Stirred by the appeal, Jack snatched the paper closer and read every word of the advertisement, his eyes dancing with interest. "Your country needs you now " it ran; and further on: "The only way to win the war is to carry it right home to the foe ""