The strange, maniacal blue owl known as the Striga has been rousted from the Great Ga'Hoole Tree. Nyra, leader of the vicious Pure Ones, is either dead or laying low in some distant land,leaving the tree finally at peace. As if fed by an invisible spring, learning and the lively arts flourish at the great tree and spread throughout the owl kingdoms. But unbeknowst to the Guardians, in a long-empty cave deep in the Northern Kingdoms two ruthless villains join forces to conjure an ancient evil, an evil that will do their bidding and wreak havoc on the world. When word of this growing malevolence reaches Coryn, Soren, and the Band, the young king knows he must do two things: First, he must return the ember to the Sacred Volcanoes, for the same subtle emanation from the Ember of Hoole that stimulates the quest for knowledge and invention at the great tree, also magnifies the powers of those who seek to destroy it and all for which it stands. Second, he must gather allies. Two armies grow. Gadfeathers, bears, dire wolves, and greenowls join with the Guardians, while on the other side ancient evil takes to the sky.

被称为 "斯特里加 "的奇怪的、疯狂的蓝色猫头鹰已经被赶出了伟大的加胡尔树。邪恶的纯种人的领袖尼拉要么死了，要么在某个遥远的地方躲藏起来，让大树终于得到了平静。仿佛有一股无形的泉水在滋养着，学习和生动的艺术在大树上蓬勃发展，并在整个猫头鹰王国传播。但守护者们不知道的是，在北方王国深处的一个空旷的山洞里，两个无情的恶棍联合起来，召唤出一个古老的恶魔，这个恶魔将听从他们的命令，给世界带来巨大的破坏。当科林、索伦和乐队听到这个日益增长的邪恶的消息时，年轻的国王知道他必须做两件事。首先，他必须将琥珀送回圣火山，因为胡尔琥珀发出的微妙能量刺激了大树对知识和发明的追求，也放大了那些试图摧毁它和它所代表的一切的人的力量。第二，他必须召集盟友。两支军队不断壮大。Gadfeathers、熊、可怕的狼和绿鸟加入了守护者的行列，而在另一边，古老的邪恶势力也开始在天空中活动。