Seventeen-year-old Iris Hollow has always been a bit odd. Something terrible happened to her and her two older sisters when they were children, and although they don't remember it, it has left a mark on them forever. Among other things, it left an identical crescent scar on each of their necks.
Iris spent most of her teenage years trying to avoid the oddities that seemed to cling to her heels. But then her eldest sister Grey, goes missing under suspicious circumstances, and strange experiences surround Iris from all sides. Horned men begin to chase her, a dead body falls from the ceiling of her sister's apartment, and ugly memories begin to creep into Iris's mind. It becomes clear that the only way to save the sister is to solve the mystery and figure out what happened to the three sisters in their childhood.
The closer Iris gets to the truth, the clearer it becomes that the answer will be dark and dangerous - and that Gray has been hiding a terrible secret from her for years.