After a wonderous flight around the Ponyville airspace leads Rainbow Dash to peruse the marketplace for anything that was just as awesome as she is, she comes across the brother of her best friend Fluttershy, Zephyr Breeze, a stallion she wanted as much to do with as being grounded from flying.
However, the multi-colored mare spotted that something was bothering the errant stallion, and as much as she dislikes him, he was Fluttershy's brother, and she didn't like to see him all... whatever that was plastered across his face, so she heads over to see what the problem was. Besides, the mare was sure that her very presence will knock the funk out of the stallion and bring him back to his usual insufferable self.
Little did she know that something was wrong with Zephyr, something very wrong.