City of the Lost by Kelley Armstrong

Casey Duncan is a homicide detective with a secret: when she was in college, she killed a man. She was never caught, but he was the grandson of a mobster and she knows that someday this crime will catch up to her. Casey’s best friend, Diana, is on the run from a violent, abusive ex-husband. When Diana’s husband finds her, and Casey herself is attacked shortly after, Casey knows it’s time for the two of them to disappear again.

Diana has heard of a town made for people like her, a town that takes in people on the run… Read more.