Mia Childs is a stranger to herself, happy to hide in the background because of her terrifying visions. At night, she dreams of Annwn where she meets an outrageous flirt called Ryder and a sense of belonging invades. However, when Mia's dreams become reality in the shape of a newcomer at school who's identical to the one in her dreams, her reality crumbles. Ryder's touch awakens her memories revealing that she is a child of Annwn, a guardian of her magical realm and the mortals. She learns that it was her visions of dwindling pregnancies causing the end of humanity and Annwn, which led her to evoke an ancient law, The Promise, which tests the power of their love and magic as a way to gain entry into the human world. Now, Mia must embrace her fears in order to fulfill her promise and save humanity because Greyson, a Darkshadow has been manipulating events from the beginning and the fate of everyone she loves lies in her hands.