The premise here is pretty interesting. A doctor is separated from his injured wife in an early WWI battle and taken prisoner. He is treated well as a prisoner of war and, believing his wife to be dead, has a child with another woman while in captivity. A few years later the war ends (this movie was filmed and released before it actually did, interestingly), and he returns home with his child and the boy's mother, only to find his wife alive, but paralyzed.

I'm not sure the way that scenario ends up in this case is completely satisfying, but you could see a modern take on it, by Petzold maybe or even von Trier, working out.