In the midst of war, Soren's sister, Eglantine, unwittingly becomes a spy for Kludd, leader of the Pure Ones, a group of evil owls. She is brainwashed by an owl sent by the Pure Ones to infiltrate the Great Ga'Hoole Tree. Her odd behavior eventually attracts attention, and Soren and his friends vow to find out what has happened. They ultimately learn of her brainwashing and help her reverse the effects. Kludd continues to battle against the Guardians of Ga'Hoole for control of their tree. In the end, Kludd and his forces are defeated, but his conflict with Soren is not yet over.

With its fascinating look at the owl kingdom and its messages about courage and loyalty, this is a great series for families to listen to together.