After the hit on The Ash and the elders, many of their under Fae pets have escaped. As Bo, Kenzi, and Hale go out hunting, they lament the fact that Dyson has been missing for weeks, not just because they could really use his help getting the wee monsters back in captivity. And when he finally does show up, he has no words for Bo. He's heartbroken at the very fact that he no longer feels any love for her, and can't bring himself to tell her.
She knows something's up, but they have bigger fish to fry: It seems a gang of Fae called the Sluagh, who are outcasts from both the Light and Dark clans, have taken the Ash's critical condition as an opportunity to claim all Light territories as their own. Bo and her team are tipped off to the plan when a Light Fae turns up dead - all of his skin pulled off of him. Before long, Lauren discovers the skin, discarded elsewhere, but the strangest part is that its bearer had a tattoo in the shape of a map tattooed inside his skin. This man was a Guardian, the kind of Faethat dedicates their lives to the protection of some great secret, so the map must have lead to something very dear, indeed.
Bo and Lauren share their research with Trick who reveals that the tattooed man, and his recently murdered counterpart - a Fae who sheathed a sword in his spine - were protecting the sacred pact The Ash had with the land. Centuries ago, The Ash made mystical love to the physical manifestation of the land on which the Light now live, creating a virtually unbreakable pact. But with the map to point the way and the sword to break the Heartstone, the seal of The Ash's pact with the land, the Sluagh may be able to take the spirit of the land by force. The only missing element is a flood of human sexual energy to give a supercharge to the power of the sacrament, such as would be felt at a pagan ritual.
Enter Kenzi. If anyone can find an underground, pagan rave, it's her. She ushers them all to the sweet spot, where Bo swiftly finds and incapacitates the leader of the Sluagh just before he's able to violate the spirit of the land. She's helped in no small part by Dyson, who finds the leader's henchman and knocks him out, keeping him from uttering the sacred incantation that seals the bond between land and lord. Before she leaves, she sees a small, quiet girl staring intently at her, and realizes she's seen this girl before.
Bo and her team have saved their land and their fates, but they realize that the Sluagh couldn't have done all this alone. The acting Ash, a man named Buzz, has been working with them in order to secure greater power for himself, and he remains a threat.
And Bo has yet more trouble in her path: After Dyson comes clean and tells her he can never love her again, the quiet girl from the rave returns with a warning. She says that something ancient has awoken and is coming for Bo, and when this mysterious force arrives, the damage will be earthshaking.