Second installment of the critically-acclaimed Sentinel Trilogy. In his desperate search for answers about the Sentinels, an ancient society of guardians that his parents once belonged to, fifteen-year-old Nicholas Hallow is tipped into a fresh nightmare of terrifying monsters - and even more sinister humans.

As Nicholas is challenged to become a Sentinel, he must track down a mysterious girl with the help of a grumpy cat. Meanwhile, an uprising of evil threatens to destroy the Sentinels and send the world spiralling into chaos.