Everything begins to come together in this episode. Hohenheim has confronted Dante and the Homunculus, but he was taken by surprise when the Homunculus of his former wife appears, and he is captured by Dante and sent to the other side of the mysterious gate. Mustang confronts the military court, not about the Fuhrer yet, but about his secretary Juliet Douglass. His words revealed him to the Fuhrer, who orders him to the front lines on the north, to make it easy to dispose of him when the time comes. Ed and Al are on the run, disguising themselves. They don't make it very far before being discovered, but they were far enough for Ed to find Sensei, who knows of his plans when he asks for a piece of her child's inactive person. Al, trusted to stay in hiding, of course runs off and meets with Tucker. He reveals Nina's motionless body to Al, who is taken by it, and offers to use himself to help her.
'Humankind cannot gain anything without first giving something in return. To obtain, something of equal value must be lost. That is Alchemy's first law of Equivalent Exchange. In those days, we really believed that to be the world's one, and only, truth'.
-Alphonse Elric
Edward and Alphonse Elric are two brothers gifted with the ability of alchemy, the science of taking one thing and changing it into another. However, alchemy works on the theory of Equivalent Exchange - for something to be created, something else of equal value must be sacrificed. When their mother dies, Edward decides to do the unthinkable - bringing her back to life by breaking one of Alchemy's biggest taboos and performing Human Alchemy. Thinking they have nothing more to lose, he and Alphonse make their attempt - but something goes horribly wrong. In the process, Alphonse loses his body and Edward loses his leg. Ed manages to save Al by attaching his spirit to a suit of armor, but at the cost of his arm and leg.