The Norwegian freighter Gangerolf leaves Subic Bay in the Philippines with a motley assortment of passengers. In the hold, under armed guard, is the entire crew of a sunken U-boat. In the first class cabins are Bill Derby, a British submarine commander on his way back to England for a medical board; Lt-Commander Witheringham - 'Withers' - a useless little man whose existence the Admiralty has forgotten over the years; and Captain Spatter, the American commander of the prisoners' guard. He's always broke becuase he plays craps with the enlisted men and never wins. But the most important passenger is Wren (Womens' Royal Navy Service) Mary Lou Smith - an unconventional young woman. Every character, from Wren Smith to Captain 'Happy' Christiansen, the Gangerolf 's huge, whiskey-guzzling Master, is real and alive, from the moment they board the freighter to the day they are marooned on a deserted island.