Blue Moon - Lee Child

It's a random universe, but once in a blue moon things turn out just right. In a nameless city, two rival criminal gangs are competing for control. But they hadn’t counted on Jack Reacher arriving on their patch. Reacher is trained to notice things. He’s on a Greyhound bus, watching an elderly man sleeping in his seat, with a fat envelope of cash hanging out of his pocket. Another passenger is watching too ... hoping to get rich quick.

Lee Child