Discord's reform depends on a now aged pony... What happens when her health fails?

Criticism encouraged.

Prairie Fire is a young artist pony who lived in Ponyville a few years before the MLP plot started up, and somehow entangled himself in the lives of several of the mane six. What will Twilight think when Applejack and Rarity describe the long-gone colt? And what will they learn from his actions? More importantly, what will -Applejack- learn about friendship and responsibility, and what it means to be a family?