Hadley Weston reunites with her secret love interest, Fitz MacGregor, in Paris, defying orders from governing officials that they remain apart. When they are mysteriously followed, Fitz must reveal an unbelievable truth: he's a witch, and so is Hadley. While she cultivates her newfound power, Hadley partners with Fitz to solve a family mystery originating during seventeenth century witch trials in Scotland. When evidence leads them to a witch raising an army in a foreign world, Hadley and Fitz are forced to make a crucial decision: align themselves with a government they distrust or allow this foreign power to utilize Fitz's ancestral magic to destroy peace with humankind.