The Shattering (Guardians Of Ga'hoole, Book 5)

Eglantine has been having strange dreams, which make her yearn for her deceased parents. Her refusal to accept their deaths makes her vulnerable to manipulation. Meanwhile, the rest of the owls of the Ga'Hoole tree having repelled one attack by the Pure Ones, which was led by Soren and Eglantine's evil brother Kludd, are trying to strategize on how to prevent another attack.