An Artificial Night — Seanan McGuire

Changeling knight in the court of the Duke of Shadowed Hills. October "Toby" Daye has survived numerous challenges that would destroy fae and mortal alike.

Now Toby must take on a nightmarish new assignment. Someone is stealing both fae and mortal children -- and all signs point to Blind Michael. When the young son of Toby's closest friends is snatched from their Northern California home and his sister falls into a coma-like state, the situation becomes way too personal. Toby has no choice but to track the villains down, even when there are only three magical roads by which to reach Blind Michael's realm -- home of the legendary Wild Hunt -- and no road may be taken more than once. If she cannot escape with all the children before the candle that guides and protects her burns away, Toby herself will fall prey to the Wild Hunt and Blind Michael's inescapable power,

And it doesn't bode well for the success of her mission that her own personal Fetch, May Daye -- the harbinger of Toby's own death -- has suddenly turned up on her doorstep...