Stubborn, plain-spoken and from an unimpressive family, Lydia Polk never expected to be accepted into the Royal Academy of Witches. Now, with Hitlers army rampaging across Europe, the witches of Britain have joined the war effort, and Lydia is key to the cause: she must use her magic to track down magical relics before Hitler and his sycophants can. When a Nazi witch infiltrates the Academy with heart-breaking consequences, the coven is left shaken, exposed and divided. The elder British witches have no interest in further loss of coven life in service of a government that has forced them into hiding for decades, no matter the consequences to the world. But with the discovery of theGrimorium Bellum,an ancient book that leaves a trail of death and destruction wherever it goes, Lydia knows her mission has never been more urgent.

Alone and woefully outnumbered, Lydia makes her way to the heart of occupied France, where she finds allies in Rebecca Gagnea fierce French resistance fighter chockful of secretsand Henry Boudreauxa handsome Haitian-American art historian with a little magic of his own. Together, they traverse the country, stalked by the natural and supernatural alike, in search of the grimoire. But, as Lydia soon discovers, finding the book is only half the battletheGrimorium Bellumhas a dark agenda all its own. Lydia must subdue it before the Witches of the Third Reich can use itbut shell have to survive the book herself, first.