In a small rubber raft in the south pacific, Cpl. Allison, USMC (Robert Mitchum) washes ashore on a small island. He quickly finds that the only other inhabitant is Sister Angela (Deborah Kerr), a nun who had been left a few days earlier with a priest, who has since died. While they have no way to leave the island, they are lucky enough to have plenty of fruit, fish and fresh water. A close bond is formed between the two, sometimes perhaps too close for a nun and a marine. However their routine is shattered when the Japanese arrive on the island to build a base and force the two into hiding.