The Other Brothers Elric: Part 2

Weakened by the red water, Fletcher buys the Elrics an escape by transmuting a tree to block the door. Mugear seizes Russell's red stone and, dropping it into a container of red water, gains the ability to transmute despite being no alchemist, binding the Tringham brothers. He reveals he has always known they are frauds, since their golden eyes and hair mark them as the sons of Nash Tringham. Back at Belsio's home, the Elrics find Elisa's cough worsening and learn the full history: Nash discovered the red water, refused Mugear's demands, then relented under pressure and researched it in the mines. Prosperity followed, but so did a spreading disease that killed infants, until the alchemist doctor Tim Marcoh saved Elisa with a mysterious stone and traced the sickness to the toxic water. Confronted, a guilt-stricken Nash vanished for good.

Mugear reveals his aim to expose pregnant women to the red water over time in order to grow a perfect stone. Playing along, Ed pretends to cooperate, destroys Mugear's red stone, and frees Russell and Fletcher from their cell while urging Russell to abandon the doomed research. Ed also deduces that Mugear murdered Nash for knowing too much. When Mugear turns his container into a gun using more flawed stones, the Tringhams' plant alchemy holds him off long enough for the Elrics to topple a pillar on him. Mugear flees through a hidden passage to the underground stream, sets a cannon trap, and is ultimately crushed by a falling boulder during the resulting cave-in. As the red water begins to overflow, Ed raises a full ring of stone walls to shield the town while Fletcher transmutes trees that absorb and neutralize the toxin, clearing it away for good.

With the crisis over, Russell vows to answer for their actions and to use plant alchemy to help Belsio's farm and revive Xenotime. He offers Ed the process for refining red water to aid his own search, but Ed declines, choosing to find his own path. On the train, Ed discovers a note in which Russell promises to become a better brother to Fletcher, embarrassing him mostly because Russell is younger yet taller.

The story adapts the franchise's first light novel, Fullmetal Alchemist: The Land of Sand. The Japanese version has Mugear confirm the impostors by their blond hair and gold eyes, while the Funimation dub instead has him recognize the real Ed by his automail arm.