When a small, red bird escapes from Canterlot, Princess Celestia writes a letter to Twilight requesting for her to find her.
There is a problem however. Fluttershy follows one of her animal friends, a bear, and finds a little filly. Fluttershy takes her home and minds her, like a mother.
But she has a secret that only Fluttershy knows. And if anyone else finds out, the little filly might be in big trouble.

Book 1: The Secret of Cinder
Book 2: Changelings can Change!
Book 3: [Spoilers!]