The film starts just after the Battle of El Alamein somewhere in North Africa. British troops train in enemy plane and ship recognition. They train to operate an inflatable dinghy and are then taken by submarine to an Adriatic island. After setting up camp they discover that the island is the base for a small unit of Germans when one of the British soldiers bumps into a German soldier while both are bathing nude in the sea. The British soldiers hunt for the Germans and find a former monastery where they are surprised by a German officer. He explains that his group were guarding stores for re-supplying German submarines but have been forgotten by their superiors and offers to share his supplies and accommodation if the British will agree to a truce. The British soldiers return to their camp to consider the offer and eventually agree to accept when they realise that their food and water are about to run out. They join the Germans at the monastery but both the British NCO Bolter and the German NCO Meister disagree. The two sides live harmoniously and even find mutual interests, with Finch befriending a German archaeologist and helping on an archaeological dig. One day, while sunbathing, the British officer Brown sees a woman, Elsa, in the sea clinging to some wreckage. He is unable to swim and calls to his men to help him but they ignore his calls. Eventually he jumps in the sea but has to be rescued by the woman. The soldiers talk to her and discover that she is Serbian and doesn't understand English, French or German. Finally Finch tries Italian and is able to communicate with her. Much hilarity ensues as the soldiers vie for her attention. The two NCOs are still suspicious and eventually leave the monastery for a fist fight. When they are too exhausted to continue they realise that they both agree that their duty as a soldier is to return to their own army so that they can continue fighting. They agree to take the inflatable dinghy and return to the war. However they are unable to overcome the current and are forced to return to the island. When the British are eventually rescued by submarine they ask to take Elsa with them and she gladly joins Finch. The Germans are rescued by submarine shortly afterwards and resign themselves to being transferred to the Eastern Front.
