Episode 11, "The Other Elric Brothers (Part 1)"
Synopsis: The Elric brothers travel to the town of Xenotime, where research is being done on the Philosopher’s Stone to replenish the gold supply. However, they find that two brothers are claiming to be them. They sneak into the mansion where the fake Elrics work and confront them, but are driven out. Later, they confront them again, and the younger brother stands up against the older one, but the guards arrive again.
Comments:
This and the next episode are adaptations of Makoto Inoue’s light novel, Sareki no Daichi (translated by Viz as "The Land of Sand"), from 2003. In it, Edward and Alphonse find themselves in the mining town of Xenotime, where they encounter fake Elric brothers, Russell and Fletcher Tringham. I haven’t read this book. I’ve only read a brief synopsis. I’m not sure whether it was intended to be part of the manga canon or not, because it also features the mysterious "red water" which becomes a big plot element of the first anime series, but the book came out before these episodes.
