Mother

Searching a library for fresh leads after exposing Cornello's fake Stone, Ed opens a primer on alchemy, and the pages carry him back to boyhood. At six and five, he and Al craft a gift for their neighbor Winry, whose fright at the alchemy leaves her in tears. Their mother Trisha, the Rockbells, and Pinako calm the girl, and on the walk home Trisha marvels at how readily her sons grasp the craft, crediting their absent father and voicing her pride. From then on the boys vie for her attention, and she keeps faith that her husband will return.

A year on, Ed admits his anger at the father he scarcely remembers, and how any mention of him saddens their mother. At the Rockbells', the brothers learn Winry's parents have left to serve as surgeons in the Ishval war, only to be killed in a surprise strike. Ed then raises the idea of a homunculus, an artificial being some scholars tie to alchemy, until Pinako cuts him off and throws the boys out for treating alchemy as the answer to everything, including forbidden resurrection.

About four years later the brothers come home to find Trisha collapsed and gravely ill; her doctor tells Pinako she may have concealed the sickness for years. Hoping their father's presence might revive her, the boys write to everyone they can reach with no reply, and she dies, her final smile revealing that alchemy pleased her only because it recalled him. Unable to face life without her, Ed and Al resolve to bring her back through forbidden human transmutation and study seriously under a teacher, Izumi.

The attempt goes catastrophically wrong: the thing they raise is not human, Ed loses his left leg, and Al vanishes, prompting Ed to trade his right arm to anchor his brother's soul to a suit of armor. Al carries the maimed Ed to the Rockbells. Roy Mustang, who has watched from a distance, arrives on one of their letters and takes keen interest in the boy who survived human alchemy, inviting a visit to Central despite Pinako's contempt for the military. Overhearing this, Ed decides to become a State Alchemist to fix his brother, accepts automail, and after a year of surgery and recovery the brothers burn down their home to leave no way back.

The episode adapts the chapters The Terror of the Teacher, The Brothers' Secret, Knocking on Heaven's Door, and Fullmetal Alchemist, and it launches the flashback arc of Ed's early days that runs through the ninth episode before the story rejoins the present in the tenth.

In the English dub, Al's actor says silicone instead of silicon while listing transmutation ingredients, though the DVD subtitles use the correct term. Al also enters water during the closing spar without harming his blood seal, an inconsistency he later avoids out of fear for the seal, perhaps because he was still unaware of the danger. The book text at the start is lifted from a review of a Dungeons and Dragons sourcebook, and the letter to the Elrics is signed with the name of English horror author James Herbert.