In Arkham, Massachusetts, the line between the haves and the have-nots is steeped in colonial tradition that stretches back over four hundred years. The Daughters of Arkham, a secret society of wealthy women, stand at the center of it all. On the surface, their power is assured by blood and money. Beneath it, they hold pacts with strange entities beyond the understanding of mortals.

Fifteen-year-old Abigail Thorndike learned many unsettling things about herself and her town in the past year. The strangest, perhaps, was discovering the existence of the Croatan, a monstrous species that has disguised themselves as humans for centuries. Some Croatan serve the sinister Daughters of Arkham. Others seek to overthrow their human masters. Abby's favorite teacher, Mr. Harris, is one of the good ones―or so Abby believed until Mr. Harris and the enigmatic Captain Virginia abducted Abby's newborn child for some alien purpose. Abby and her friends will stop at nothing to get the child back.