The first British film about WWII prisoners of war is still the best. It introduces what would become the standard motifs of the POW film: the suspicion of a German mole; the escape detail; the concert party; and the irregular lifeline of letters from home, and Red Cross parcels. But The Captive Heart excels because, apart from the reportage, there is also a great premise.
This was loosely based on actual events. A Czech dissident (Michael Redgrave) escapes from Dachau and adopts the identity of a dead British officer. Then is taken prisoner. As part of his cover he begins to write to the wife of his new identity, unaware the two were estranged. And they fall in love with each other, with her ignorant of the deception.
The soldiers are taken prisoner after Dunkirk and incarcerated until the end of the war. The film reflects on the psychological and emotional consequences. Often this is sentimental as they idealise home. Jack Warner is the heart of the ensemble support cast, but it's Redgrave's repressed trauma that cuts deepest.
Some of the actors had actually been POWs, and part of the location shoot was at a real stalag. But while there is realism, the mood is lyrical. This is a hugely moving film. What emerges most starkly is the prisoners' fear of being forgotten. And an impression that in a time of such instability, miracles really do seem to happen.