After Pearl Harbor, convicts at Alcatraz prison live in fear of bomb attacks, driving Champ Larkin and his pal Jimbo to a desperate escape attempt which lands them on a tiny lighthouse island, where they take over. The five inhabitants are stymied in their efforts to summon aid. But the island also figures in the schemes of a big Nazi spy ring; which will win out, the gangsters' greed or their patriotism?

Dos prisioneros escapan de la famosa prisión de Alcatraz y se refugian en un faro utilizado por espías nazis. Con su gran honestidad, el farero y su hija se ganan la confianza de los dos fugitivos, quienes sacrificarán su libertad para salvar a la ciudad de San Francisco de un ataque submarino.