An accident at the Wonderbolt Academy occurs, and many pegasi, including the Wonderbolts, are killed. Rainbow Dash was one of the ponies killed.
Scootaloo, who is distraught over the news of the accident, goes home to find a note from Rainbow Dash herself, proclaiming that she is indeed alive.
Scoots proceeds to give up her life of crusading and finding her cutie mark to find Rainbow Dash, even if she can't fly or doesn't have meaning in her life. She is determined to find her big sis, even if it means giving up every dream she ever had.