Everybody knows Cate Cahill and her sisters are eccentric. Too pretty, too reclusive, and far too educated for their own good. But the truth is even worse: they're witches. And if their secret is discovered by the priests of the Brotherhood, it would mean an asylum, a prison ship--or an early grave. Before her mother died, Cate promised to protect her sisters. But with six months to choose between marriage and the Sisterhood, she might not be able to keep her word... especially after she finds her mother's diary, uncovering a secret that could spell her family's destruction. Desperate to find alternatives to their fate, Cate stars scouring banned books and questioning rebellious new friends, all while juggling tea parties, shocking marriage proposals, and a forbidden romance with the completely unsuitable Finn Belastra. If what her mother wrote is true, the Cahill girls aren't safe. Not from the Brotherhood, the Sisterhood -- not even from each other.