In the final days of the battle of Manila during World War II, fanatical Japanese naval forces barricade themselves inside the walls of Intramuros, the ancient Spanish walled city of Manila. In a suicidal last stand, the Japanese hold many thousand Filipinos captive within the fortress, despite the incessant bombardment of United States artillery. An American war correspondent, Murray, arrives at the front line where a guerrilla unit led by American Lieutenant Sorenson makes contact with a young Filipino fighter, Nardo, who has escaped the fortress through a sewer passage. Nardo proposes a plan to rescue the prisoners through the tunnel.