Heaven Knows, Mr. Allison

A U.S. Marine reconnaissance party is spotted and fired upon as they disembark from a Navy submarine in the South Pacific. The submarine captain is forced to dive, leaving the scouting team behind to fend for themselves. The immediate threat forces them to improvise survival on the surface.

Allison reaches a rubber raft and drifts for days until he lands on a small island. He discovers an abandoned settlement and a chapel with a single occupant, Sister Angela, a novice Irish nun who has been on the island for four days.

Angela explains that she arrived with an elderly priest to evacuate another clergyman, but the Japanese had arrived first. The priest dies, and the natives who brought them to the island vanish without warning. The pair then faces life alone on the abandoned settlement.

A detachment of Japanese troops arrives to set up a meteorological camp, forcing Allison and Angela to hide in a cave. They must avoid detection while guards establish the camp.

Angela cannot stomach the raw fish Allison catches, so he sneaks into the Japanese camp at night to obtain supplies. He narrowly avoids detection and returns to the cave with what they need to survive.

That night they watch flashes from naval guns firing in a distant sea battle. The island remains tense as war rages beyond the horizon.

The Japanese depart unexpectedly, and Allison professes his love and proposes marriage. Angela shows her engagement ring and explains that it symbolizes her forthcoming final holy vows.

Allison gets drunk on sake and blurts that her devotion seems pointless in their isolation. She rebukes him, then runs into the tropical rain and falls ill; he finds her shivering and carries her back.

The Japanese return, forcing them to retreat to the cave. Allison later sneaks into the camp to fetch blankets; a guard discovers him and he kills the soldier, triggering alarm. The Japanese respond by setting fires to the vegetation to flush them out.

When a Japanese soldier discovers the cave, Allison and Sister Angela face surrender or death. The explosion that follows is not a grenade but a bomb, signaling that American bombardment has begun for the island landing.

During the bombardment, Allison feels guided by a message from God and sabotages all four artillery pieces by removing their breechblocks. The action saves many American lives, but he is wounded and the breechblocks go missing before the landing.

After the landing, Marine officers are puzzled by the missing breechblocks. Allison and Sister Angela say goodbye as the Marines begin occupation, with Allison coming to terms with Angela's devotion and their enduring companionship.

Allison is found and transferred by Marines to the ship, with Sister Angela walking beside him. The scene closes on their quiet pledge that they will remain close friends and companions despite the separation.