Shortly after the Sonic Rainboom that led to her getting her Cutie Mark, Pinkamena Diane Pie's long lost sister Blueberry Swirl manages to find her after spending most of their lives apart, and she convinces Pinkamena to leave the Rock Farm. Now certain on who she wants to be, Pinkamena agrees to go with her and the two set out for Ponyville in this prequel to the events of Friendship is Magic.