A woman, a PI -- living in California, rejoicing in the name October Daye and going by Toby, doing her best to forget with her fiance and daughter that she's half fae -- is tracking down an abduction of her liege lord's wife and daughter. Except that she's caught by her suspect and turned into a fish. If someone hadn't tossed her into the pool, she would have died. Even as it was, she lost fourteen years, and so her whole life.
After she is lurching along, trying even harder to pretend that she has no connection at all to the fae, she comes home one night after her job as a cashier. Getting caught by the dawn, and having to hide in an alleyway where Tybalt the King of the Cat Sidhe harasses her does not keep her from getting there, but while she sleeps, she gets messages on her answering machine.
Evening, the fairy woman who had retrieved her from the police after her reappearance and looked after her those first days, had left them. She had been murdered. And in the last one, she cursed Toby to investigate it and deal with the murderer, or die.
Notifying the local Queen enrages the queen, and ensures she gets no help there. Toby must investigate on her own, and finds herself pulled back into the fae world in the course of a novel that involves falling into the sea, panicking, and being rescued by a selkie; hero-worship; roses made out of glass; a place where Toby had lived with others as runaways on the margins of society; meeting again with her liege lord; a key made mostly of roses and a powerful magical thing; and two cats and a rose goblin.