The Boy Allies with the Terror of the Seas; Or, The Last Shot of Submarine D-16

The narrative follows two young officers, Jack Templeton and Frank Chadwick, who serve aboard a British submarine equipped with an experimental system allowing prolonged submergence. They undertake a series of naval operations against enemy warships, sinking a foe and probing blockaded waters, while confronting onboard danger, espionage, capture, and daring escapes. Their service carries them from the North Sea into the Baltic and Mediterranean, through raids, close-quarters combat, and covert missions that expose plots and neutrality violations. Episodes alternate action at sea with schemes ashore, culminating in a final confrontation in which the submarine fires its decisive last shot.