We quickly learn that the commandant at Wintersborn is none other than Rauffenstein, who was badly injured when his plane was shot down, and he now wears a steel corset and moves with difficulty. The commandant soon greets the incoming Marechal and Boeldieu, who have repeatedly attempted to escape from other POW camps. Rauffenstein warns the Frenchmen, "Gentlemen, I respect your patriotism and courage. But the situation is completely different here. No one escapes from this fortress."

Marechal and Boeldieu are assigned to the same room as Rosenthal, who is already at Wintersborn, and the three French officers immediately start to plan an escape. Meanwhile, the melancholy Rauffenstein greatly enjoys the company of Boeldieu because both the German and the Frenchman come from titled aristocracy. At one point, Rauffenstein tells Boeldieu, "I don't know who will win this war, but whatever the outcome, it will mean the end of the Rauffensteins and the Boeldieus."

Eventually Boeldieu realizes that the only sensible escape plan at Wintersborn involves one man creating a diversion while two others descend a long rope and run away. In the film's dramatic high point, Boeldieu dons his white gloves and plays a flute as he taunts the reluctant Rauffenstein into shooting him. During the commotion, Marechal and Rosenthal escape. As Boeldieu lies dying, he tells the heartbroken Rauffenstein, "For a commoner, dying in war is a tragedy. But for you and me, it's a good way out."

What might be thought of as Act III is the 25 minutes of the film that chronicles the 200-mile trek that takes Marechal and Rosenthal from Wintersborn to the Swiss border. Along the way, Rosenthal badly sprains his ankle, and Marechal considers abandoning him and starts to walk away. Then Rosenthal starts to sing "Un Petit Navire," a silly song about a little ship, and this plays on Marechal's emotions, causing him to come back for the injured Rosenthal.

Perhaps thirty miles short of the Swiss border, the exhausted escapees take refuge on the farm of a kindly German war widow named Elsa (Dita Parlo), who has only her five-year-old daughter Lotte to keep her company. There, while the two Frenchmen recover their health, Marechal and Elsa fall in love, even though neither speaks the other's language. The little celebration on Christmas Eve of Elsa, Lotte, Marechal, and Rosenthal is sublime, as Renoir shows us four people who differ in nationality, language, social class, ethnicity, gender, and age sharing a magical evening. Later, as Marechal departs the farm, he tries to reach out to Elsa by remarking on her little girl's blue eyes by saying, "Lotte hat blaue Augen." But in what will probably be Elsa's last words ever to Marechal, she gently corrects his grammar, "Blauen Augen."

In a couple of days, Marechal and Rosenthal arrive at the Swiss border, but as they make their move to cross, a German border patrol arrives and starts firing at them. But the soldier in charge of the patrol soon shouts, "Don't shoot! They're in Switzerland!" One of the German soldiers who had been firing lowers his gun and says the movie's last line: "Good for them!" The film's last image is of Marechal and Rosenthal slogging through snow towards a Swiss village.

La Grande Illusion is a complex film, and it seems to me that it's helpful in thinking about the movie to keep its historical context in mind. The story is set during World War I, a time when Renoir served in the French military, and he surely drew upon things he saw and heard during that war when he made the film about 18 years later. On the other hand, at the time of the movie's release in 1937, Hitler's power was firmly entrenched and the storm clouds of World War II were gathering. It's worth noting that world leaders in the late 1930s perceived La Grande Illusion to be highly politically charged. The film's unabashed internationalism was probably an important motive behind U.S. President Franklin Roosevelt's public praise of it, and its favorable treatment of a Jewish character was probably the main reason that Nazi propaganda minister Joseph Goebbels declared it to be "cinematographic enemy number one."