With her grandfather acting as the Overseer for an ancient group of human-like people called Akori, Addison Sanders life is pretty complicated.
After a strange man is spotted lurking around the estate they live at, concerns arise that maybe the humans who killed her parents have decided to come back for her. She's forced to have Gage, an Akori she grew up with, as her shadow. They used to be friends, but a few years earlier he suddenly quit acknowledging she was even alive and she's not exactly thrilled he's suddenly back in the picture.
Addy comes across Tanner on the beach one night. He tells her that he can see the things about her and the place she lives that no humans outside of her family should be able aware of. He wants to leave, but he can't. A strange pulling is driving him to be near the Akori.
As the last living Sanders, Addy is forced to try to claim her grandfather's position as the Overseer after he dies. Instead of inheriting his position, a strange Akori symbol appears on her neck. It's a mark no human should be able to carry.
Addy sets out on a journey that changes everything she though she knew about her life. She discovers her family was deceived into serving the Akori for the last 250 years. The mark leads her to a stranger who may turn out to be the key to ending her family's centuries old burden.
Every decision she makes could set her and the Akori people on a course for disaster. She must decide if the price of breaking the oath is worth the devastation it will cause within the Akori people.