Everline Blackthorn has devoted her life to the wardens - a fierce sect who wield arcane magic to guard their community against vampiric monsters known as the vespertine. When a strangely human vespertine is killed on their borders, and a series of unsettling events follow, Everline disobeys orders and uncovers a startling truth in the form of Ravel Severin: a rogue vespertine who reveals that monsters have secrets of their own. Everline's own magic has failed to appear, and she is feeling both outcast from her own community and powerfully drawn across the vespertine-fllled moors. As Ravel also needs Everline as cover to return home, he promises to use his magic to ensure safe passage for them both for the treacherous journey, but at a heavy price: vespertine magic requires blood, and Everline will have to allow Ravel to feed from her.