The Red Glow

Twenty-first in the 2003 series, this chapter converges several threats on the fifth laboratory as Scar's arrival accidentally frees the buried homunculus Greed and unleashes a horde of caged chimeras. Edward, guided deeper by the surviving Slicer, runs into the supposedly executed Shou Tucker, now fused with a chimera body, and a hoard of unfinished red stones that put the temptation of real power directly in his hands.

As Barry taunts a self-doubting Alphonse, Scar drops into the yard, tears off the Chopper's arm, and is stalled just long enough for Barry to trigger a hidden bomb that shatters Greed's decades-old seal. The freed homunculus throws open the prison's locks and offers escape to the chimeras held below. Deeper inside, Edward can only watch as the younger Slicer destroys his own blood rune, and the elder agrees to guide him onward. Next door, tremors rouse the prison as the Crimson Alchemist Zolf Kimbley is pulled from his cell for a military experiment, with Envy wearing Basque Grand's face to escort the inmates. Chimeras ambush the wounded Edward until a whistle calls them off, revealing Shou Tucker, alive and merged with a beast body, still chasing a way to remake his dead daughter Nina. Elsewhere Scar recounts to Alphonse the day his brother broke the taboo of human transmutation before Lust and Gluttony interrupt them. Tucker leads Edward to a chamber of refined red water and explains that no ordinary alchemist can finish the stone, at which Edward realizes with dread that he may be capable of completing it.

The episode adapts the chapters The Definition of Human and Fullmetal Body. Screenwriter Sho Aikawa expanded the Laboratory 5 storyline here, folding in Scar, Greed, and Kimbley to broaden the cast and seed later plots, and structured the hour around parallel confrontations, pairing Alphonse with Scar and Edward with Tucker, to enrich the narrative.