Two young sailors aboard a torpedo-boat destroyer become involved in espionage and naval action after an encounter with a suspicious foreign agent. Their service brings rescues, secret missions, investigation of a derelict, a drum-head court-martial, bombardments, torpedo attacks, capture and imprisonment, and a climactic sea engagement followed by operations ashore and a return home. The narrative emphasizes loyalty, courage, resourcefulness, and duty as the youths undertake strategic tasks, face moral and physical tests, and perform daring deeds that shape their fortunes and reputations.