Make Me by Lee Child

Reacher finds himself in the small town of Mother's Rest as he's passing through on his way to Chicago. While there, he meets an ex-FBI agent named Michelle Chang who is trying to trace the whereabouts of a co-worker named Keever. Chang doesn't know why Keever was in Mother's Rest or what he was investigating, but Reacher agrees to help Chang find him. Their journey takes them around the country and is a puzzle where they are forced to confront the very dark side of human nature.  Make Me is fast-paced and not for the squeamish.