Matilda and Pearl (Unicorn Academy, Book 9)

Matilda loves to have fun. She's not too worried that her unicorn, Pearl, hasn't found her magic yet. She also loves her friends at Unicorn Academy--even when they get annoyed at her for being disorganized. But there's a problem so big that even Matilda can't ignore it. On a camping trip, she and Pearl see someone hurting the oldest tree on Unicorn Island. Can Matilda and Pearl find out who it is, and save the tree?