Bone Crossed is the fourth of The Mercedes Thompson Series. It starts off with Mercy’s mom showing up when Adam’s over and then Stefan dropping into the middle of her living room flayed, starved, burned, and almost unrecognizable. He warns Mercy that Marsilia, his Mistress, knows about Mercy’s involvement in the death of one of her favourite vampires. He tells Mercy to run. Considering who Marsilia is, it’s something that gets considered. Considering who Mercy is though, regardless of panic attacks left over from the rape in the precious book, it’s all strategic and not really about running away.
The vampires have put a magical skull and cross bones on the door of Mercy’s garage that mark Mercy as an ally-turned-traitor. When Stefan is recovering from the torture he went through at Marsilia’s hands, he accidentally floods Mercy’s mind, and Adam brings her into the pack to snap her out of it.
Then, while out on a date, the vampires set up a trap for the werewolves at Uncle Mike’s, which means that Adam and Mercy come running. The fallout is the death of Mary Jo, one of Adam’s wolves, and her return to life through the intervention of Baba Yaga on behalf of Mercy. The wolves decide that the only way to barter peace with the vampires is to get Mercy out of town for a bit, so she goes to see her old college buddy (Amber) who claims that her house in Spokane is haunted. The only snag is a vampire named Jim Blackwood, a.k.a. The Monster. Now, as he’s nightmare that scares the other nightmares and the characters all think Mercy won’t run into him, you know she’s going to meet him on her first night in Spokane.
While in Spokane, Mercy finds ghosts, exchanges blood with the Big Bad twice, finds out that her friends are involved with Blackwood, and saves the life of Chad (Amber’s amazingly funny deaf son). Stefan shows up to take her home and Amber’s family goes to a hotel.
On her way back from Spokane, Stefan takes Mercy on as a “sheep”, which is important for the vampire subplot where Marsilia is playing rather brutal seethe politics with some of her unhappy vamps and the acceptance (or lack thereof) of Mercy into the werewolf pack.
After peace is brokered between the wolves and the vamps Mercy gets kidnapped and winds up with Blackwood again while Amber, her husband, and her son are in his power. Mercy has ghosts, an evil vampire, and a zombie to deal with while being held with her friend’s family and an Oakman. The question is, how will she escape and how many will survive when she does?