Kieran's job of being a guardian angel is straightforward: observe and learn—and don't intervene in their lives. But then he watches as his first charge dies at the hands of evil while he does nothing to help.

Overcome with grief and doubt, Kieran flees back to the safety of heaven. With guidance from his mentor, he learns all he can about the Battle of the Fallen and the creation of evil itself. With renewed determination, he vows he will save the Ordinaries in his care.

The rules of being a guardian angel have not changed, but Kieran has. Returning to earth, only Kieran knows how essential it is to find and protect one 17-year-old girl. The girl who can thwart the Devil's escape from his prison and the start of Armageddon.