The Midnight Line by Lee Child

JACK Reacher – giant, righteous avenger, seeker of the truth – sees a West Point class ring from 2005 in a pawn shop window in a Midwestern town. The ring must have belonged to a woman. He pledges to track her down. Curiosity sends him on a quest involving human damage, stolen prescription drugs, a private eye, a drug operator who wants Reacher dead, and a man who died in the wilds of Wyoming, eaten by a bear.