Morgan Tenpenny has retreated from her painful, magical past, choosing to live quietly as a guardian of one of the gates between worlds. But her sister Gwen is married to a lord of the High Court of Faerie-and when Gwen asks her to protect her nieces, it's time for Morgan to emerge from her seclusion. The gates to Faerie have inexplicably closed, and no one knows why, not even Falcon, the fae Morgan finds trapped on her side of the gate. As a devastating illness that only affects magic users starts to sweep through the country, Falcon tells Morgan of a way to reach her nieces in Faerie through a mysterious place called Strangehold-if Morgan can trust that Falcon is all that he seems. But with the Queen of Faerie increasingly defensive of her borders, even their combined powers may not be enough to win them through. With relations between fae and human falling apart and a deadly illness threatening all of her old colleagues, Morgan finds that her past isn't as dead as she'd thought. She must navigate the threats in time to save her nieces-and just maybe the world.