Holden told Olivia it was only a matter of time before Hell came for them. After all, one doesn’t just walk away from the life he lived unscathed, but the longer Hell waited, the more Olivia let down her guard. She believed maybe happily ever after was possible—he knew it wasn’t. But when Baker shows up beaten and bloody on their doorstep with a message, all hope evaporates. The jinn make Holden an offer he can’t refuse: convince Olivia to free them all and the jinn will fight Hell alongside them. However, if their past has proved anything, it’s that the jinn cannot be trusted. When Olivia starts hearing a voice that no one can identify and Baker isn’t acting like himself, he is forced to make a decision. With Heaven staying hands off, Holden considers accepting the jinn’s offer behind Olivia’s back. One thing is clear, with their lives and the lives all those they hold dear at stake, something has to be done. If it were as easy as Holden going back to the jinn, he would do it in a heartbeat, but Hell wants more than his soul this time—they want Olivia’s too.

Olivia’s once-shining light now blazes with the fury of an avenging angel, leaving ruin in her wake. Gone are the days of soft hearts; endless compassion doesn't win wars with Hell. Without an anchor to his human self, the jinni side of Holden grows stronger every day. Giving into his true nature might mean losing the one thing worth living for, but it's the only way to stop the rise of a darkness even the angel cannot defeat. Every decision they make to re-establish balance in their world causes ripples through the universe, changing paths and intentions of even the most stalwart of friends. All it took was a single death to make waves through the Abyss. Now the lives of five people have been changed forever. No one will make it through unscathed.

Olivia and Holden always beat the odds. Destined to be apart, there was nothing they wanted or fought for more than simply to be together. But no matter how great their love, the hurt they've caused each other may be more than they can bear. An evil like no other has risen from the underworld, leaving nothing but death in its wake as it seeks out the one thing it complete and utter submission from the jinn. Losing the angel has left Olivia weakened beyond repair and unable to help even herself. Frustrated with her loss of power and devastated by her part in the death of two cherished loved ones, she struggles to find the hope she once relied on even though her relationship with Holden is crumbling. An offer to help comes from an unexpected source, but it isn’t without cost. To save herself, she will have to give up everyone else. Holden’s powers are stronger than ever before, but his control slips further and further from his grasp, putting everyone around him at risk. Unable to forgive himself or Olivia for the death of a friend, he focuses on the only thing that insuring the freedom of the jinn. But as his past comes back to haunt him, he is pushed further and further into the darkness. In their final battle between good and evil, no one is safe and everything will change.