Fullmetal Alchemist Season 1 Episode 21 The Red Glow

Edward, Alphonse, and Winry arrive in the boomtown of Rush Valley, renowned nationally for its high-quality automail craftsmanship. As the Elric brothers start to have Ed's automail repaired, they bump into two men in charge of a traveling circus. They are named Dominic and his young apprentice, Richard, who recognized Edward as the "Fullmetal Alchemist" who they had heard so many rumors of.

The group quickly befriends the oddball performers and put on a show for a traveling audience, but they soon learn that something is off with the mechanical automail legs used by Richard in his performance. Upon close inspection, Edward discovers that the legs were made from materials with a vague red glow, just like the happenings in Xenotime. The group continues their investigation after the townspeople make numerous complaints to the circus troupe due to their performance not meeting its expected standards.

Ed and Al are with Richard during another performance at night only to witness the automail legs being used in the performance malfunction and severely injure Richard. They immediately take him to the hospital where the doctors explain that this was a recurring issue with this particular design and it has injured many others. They also reveal that the red glow is brought about by a mysterious alchemical reaction known as the Red Stones.

As the brothers investigate further, they cross paths with locals who are being used as pawns in a new plot involving the theft of rare Red Stones, a process that Richard and Dominic are a part of in an attempt to collect more money for their circus show. This leads to a fierce battle between the Elric brothers and the master thief responsible for the heist.

Meanwhile, Winry is trying to build a brand new automail arm for Ed with the superior materials they found in Rush Valley. They also finally address the reason they are in Rush Valley, which is for Ed to fix the damaged automail which got destroyed after their last encounter with Scar.

The episode ends on a cliffhanger as the thief from the town enters a room that contains more Red Stones than he could have ever imagined in his wildest dreams. The audience is left wondering what his next move is going to be as Ed, Al, and Winry aim to find out what exactly the Red Stones are and why they're causing so much trouble.