An Artificial Night (October Daye)

Toby Daye-a half-human, half-fae changeling-has been an outsider from birth. After getting burned by both sides of her heritage, Toby has denied the fae world, retreating to a "normal" life. Unfortunately for her, the Faerie world had other ideas... Now her liege, the Duke of the Shadowed Hills, has asked Toby to go to the Country of Tamed Lightening to make sure all is well with his niece, Countess January O'Leary. It seems like a simple enough assignment-until Toby discovers that someone has begun murdering people close to January, and that if the killer isn't stopped, January may be the next victim.