Episode 44: Hohenheim of Light (2003 series)

Synopsis
With the mastermind behind the seven sins organizing a plan to capture the boys as well, Ed and Al must convince Mustang's faction that the Fuhrer is not what he seems. The strange reappearance of their father only complicates things further, as we learn he has his own score to settle.. one that goes to the root of this 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 a later episode that the dating system based on the birth of Christ was once used by an "ancient religion".