On Christmas Eve, Commander Gray Pierce returns home to discover his house ransacked and his pregnant lover missing. The only witness, his best friend’s wife, Kat, is found unconscious on the kitchen floor. Left in a semi-comatose state, she cannot speak—until a brilliant neurologist offers a radical approach to “unlock” her enough to answer questions. But what is learned sets Sigma Force on a frantic search tied to mysteries tracing back to the Spanish Inquisition and to a Medieval document, one of the most reviled and blood-soaked books in human history, the Malleus Maleficarum, or the Hammer of Witches. The answers in the past will reveal a frightening truth in the present, and a future teetering on the brink of apocalypse, where humanity must confront the ultimate question: What does it mean to have a soul?