Father

Gluttony and Alphonse tumble into the underground chamber of Father, whose face startles Al with its likeness to Hohenheim. Gluttony convulses as a false gate tears open and vomits out Envy along with Edward and Ling. Ed and Al's joyful reunion is brief, as Father studies the pair and names them. Learning that Hohenheim is their father and that the Elric surname comes from their mother, Father seems intrigued, then mends Al's missing armor hand and Ed's broken arm and ribs, an act that flouts equivalent exchange entirely.

Ling, sensing the being's menace and judging him no better than the children who abuse humans, moves to fight. Father brushes the prince aside and commands Gluttony to swallow him. Al warns Ed that this is the maker of every homunculus, and a scuffle erupts. Ed spots that Father transmutes without lifting a finger, and a single counter cancels the brothers' alchemy outright, a disruption Scar, May, and Hohenheim all feel from afar, leaving Ed and Al defenseless against Envy.

Envy admits he never meant to honor his bargain with Ed and that the homunculi never troubled to learn the source of their own power. Curious about Ling's spirit, Father opens a hidden eye in his brow and pours out a red fluid Ed recognizes as a Philosopher's Stone. Warned the change could kill him, Ling orders Ed to hold his fire, since obtaining a Stone was his whole purpose. The fluid seeps through the cut on his face, and after a struggle he meets Greed and willingly yields, unwilling to waste Lan Fan's sacrifice. The new Greed takes over with no memory of Dublith or of the Elrics.

Scar breaks in, having killed a guardian chimera, and Shao May rejoins May Chang. May is crushed to find the fabled Fullmetal Alchemist is the short boy she met the day before. Scar's decomposition still works on Gluttony, baffling Father, and once Ed reveals Envy's role in sparking the Ishval war, Scar turns his fury on the lair. May's alkahestry frees the brothers from Envy's grip, though their own alchemy stays sealed. Al shields the wounded May and flees through the sewers with her and Shao May, but the guardian chimeras cut them off as Envy and Gluttony close in.

The episode adapts the chapters Signpost of the Soul, The Fool's Struggle, The Avarice of Two, and The Lion of the Round Table. Unlike the manga, it only hints that Trisha and Hohenheim were never wed rather than stating it plainly. After Scar ignites hydrogen gas and escapes, Gluttony's Stone finally gives out from dying too many times, and Father later extracts it to rebuild him with his memories intact.

In the Funimation dub, Troy Baker replaces Chris Patton as Greed because Patton left voice work before recording finished, a switch some viewers read as a continuity slip since the new Greed is meant to be the original. During the first Adult Swim airing, the closing scene of Father reviving Gluttony was trimmed, likely to reclaim commercial time.