The Midnight Line by Lee Child (Jack Reacher #22)

Jack Reacher is having a bad day.
It would be a dumb idea to make it worse.
Reacher sees a West Point class ring in a pawn shop window. It's tiny. It's a woman cadet's graduation present to herself. Why would she give it up? Reacher was a West Pointer too, and he knows what she went through to get it.
All he wants is to find the woman.
He'll have to go through bikers, cops, crooks, and low-life muscle.
If she's ok, he'll walk away. If she's not ... he'll stop at nothing.
Best advice- stay out of his way.