For different reasons, Irish Catholic nun Sister Angela and U.S. Marine Corporal Allison are stranded on deserted Tuasiva Island in the South Pacific in 1944, the island abandoned due to circumstances of World War II. Calling each other Mr. Allison and "ma'am", they are respectful of each other's vocation - and of each other as people - despite their extreme differences in backgrounds and outlooks. Despite a bounty of fresh food on the island (tree fruit, fish and other game) and the hazards of the trek, they plan on using Allison's marine raft to sail 300 miles south to Fiji. This plan is thwarted when the Japanese first bomb the island, and then set up what looks to be a weather station, forcing Allison and Sister Angela into hiding. When action in the Pacific Theater makes the Japanese leave the island as quickly as they landed, Allison suspects the Allied forces won that battle and will soon be doing their own reconnaissance in the area. Thinking that they may soon be rescued, Allison tells Sister Angela what is in his heart, especially in light of the fact that Sister Angela has not yet taken her final vows: he has for the first time in his life fallen in love, and wants to marry her once off the island. Sister Angela tells him that she is already engaged to her life to God. Allison takes Sister Angela's answer hard. When the Allied forces don't show up, Allison thinks they may be stranded on the island forever, convincing Sister Angela to at least reconsider their collective lot in life. However, the war continues around them, making the twosome take life one moment at a time for however long they will be on the island.