|The Brothers' Secret|
|Title||The Brothers' Secret|
|U.S.A. Release Date||January 3, 2006|
|Preceded by||Chapter 20: The Terror of the Teacher|
|Followed by||Chapter 22: The Masked Man|
The chapter starts off with Izumi asking the boys what had happened to them since they had left her training. This results in a flashback to when their father left, to when Winry's parents died, to when their mother died, to when they tried via alchemy to bring her back, and finally to when Ed enlisted in the military.
At a young age the Elric brother's showed and affinity for alchemy. From the books their father had left behind when he left them and their mother the boys started to teach themselves the science of alchemy. Their mother, being very proud of their accomplishments, encouraged them to continue. Unexpectedly she died and the boys were forced to come to terms with that death. Unfortunately they were not able to do so and made a pact with each other that some day they would bring their mother back to life through alchemy. Granny Pinako becomes the boys' guardian and while living with her and Winry they worked ever harder to teach themselves, but eventually realized that they could only go so far teaching themselves. During a freak rainstorm that was producing catastrophic flooding that was threatening their village Ed and Al decided to try and use alchemy to create a barrier to keep the flood waters out. Before they could attempt this, however, Izumi shows up and creates an enormous barrier blocking the flood water and saving the town.
The boys seeing this determine to make Izumi take them on as apprentices. She initially rejects their plea, but finally relents to take them on if they prove themselves worthy during a one month trial period. The boys, Izumi, and her husband Sig head back to Dublith to begin their trial period training. Izumi takes the boys to a small island in the middle of Kauroy Lake. This island, Yock Island, is where they will spend the next month surviving with nothing more than a knife. There is no shelter, no wells, nothing that might ease their stay. As well, they are prohibited from using alchemy while there. During their first night they are awoken when a gigantic monster attacks them in their sleep.
- Ed references a movie where a "man performed a transmutation while a fly was in the circle" which turned him into a "fly-man". This might be a reference to the classic American Sci-fi Horror movie The Fly.