Episode 44: Hohenheim of Light (2003 series)

Synopsis
Ed and Al must convince Mustang's faction that the Führer isn't what he seems. The reappearance of their father complicates matters. He has his own score to settle -- one that goes to root of the entire conspiracy.

Trivia

 * At the beginning of the episode, Lyra discusses a religion that is now extinct in the world of Amestris. It is strongly implied that said religion was Christianity, especially given Izumi's comment in two episodes later that the dating system based on the birth of Christ was once used by an "ancient religion".