The Other Brothers Elric: Part 1

Acting on a tip from Psiren back in Aquroya, the Elrics travel to Xenotime believing the worn-out former gold town may hold a route to the Philosopher's Stone. Edward suspects locals are trying to transmute gold with it. Shortly after arriving, they use alchemy to free a small girl named Elisa from beneath a toppled mine cart. At a tavern that night, Ed suffers the familiar indignity of being taken for the younger sibling, and Elisa's uncle Belsio turns up amid family tension over the accident. When the boys finally name themselves, the villagers eject them, insisting the genuine Elrics are already working for a wealthy man named Mugear.

Furious at the theft of their identity, Ed and Al slip into Mugear's mansion and are confronted by the counterfeits. Russell Tringham, posing as Ed, needles the real one over his height, and their evenly matched duel reveals that Russell can transmute without a circle thanks to a stone in his possession. Guards force the true brothers to withdraw. Inside, Fletcher Tringham, the false Al, wants to abandon the ruse, but Russell insists on completing and claiming credit for the work their father began.

Deep beneath the estate, Mugear meets with Lust in a chamber where the red water is stored; she warns that the Elrics will not give up easily and urges retreat, but he begs for more time to finish the stone. Belsio, indifferent to who the boys really are, shelters them and explains how Mugear's wealth keeps the town under his thumb. The next day Fletcher quietly aids Al at the pharmacy, and the two bond over their hot-tempered older brothers. Al presses him to stop Russell if his path is wrong. Determined to learn the truth, Ed burrows underground into the mansion and reaches the spring, where he identifies the red water from a book as the ingredient behind a flawed version of the stone. The toxic fumes sicken him until Fletcher rushes in and saves him. Fletcher tearfully admits the red water is what causes the town's illness. Russell arrives to defend his father's legacy and battles Ed, weaponizing a pipe of pressurized red water, until Fletcher throws himself into the blast and reminds his brother that their father meant the research to heal, not harm.

The story adapts the franchise's first light novel, Fullmetal Alchemist: The Land of Sand. As a small continuity slip, Ed could have settled the whole identity dispute simply by producing his State Alchemist pocket watch, exactly as he had done in the previous episode.