With the Brotherhood persecuting witches like never before, a divided Sisterhood desperately needs Cate to come into her Prophesied powers. And after Cate's friend Sachi is arrested for using magic, a war-thirsty Sister offers to help her find answers—if Cate is willing to endanger everyone she loves. Cate doesn't want to be a weapon, and she doesn't want to involve her friends and Finn in the Sisterhood's schemes. But when Maura and Tess join the Sisterhood, Maura makes it clear that she'll do whatever it takes to lead the witches to victory. Even if it means sacrifices. Even if it means overthrowing Cate. Even if it means all-out war.