The only one left : a novel
Riley Sager
Aidan Thomas has murdered eight women and there's a ninth he has earmarked for death: Rachel, imprisoned in a backyard shed. When his wife dies, Aidan and his daughter Cecilia are forced to move, he brings Rachel along, introducing her to Cecilia as a "family friend," betting that after five years of captivity she will be too brainwashed and fearful to attempt to escape.