Darkfever (Fever, #1)

When her sister is murdered, leaving a single clue to her death—a cryptic message on MacKayla Lane’s cell phone–Mac journeys to Ireland in search of answers. The quest to find her sister’s killer draws her into a shadowy realm where nothing is as it seems, where good and evil wear the same treacherously seductive mask. She is soon faced with an even greater challenge: staying alive long enough to learn how to handle a power she had no idea she possessed—a gift that allows her to see beyond the world of man, into the dangerous realm of the Fae.