Blue Moon - Lee Child

Jack Reacher is a former military cop, 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... obviously hoping to get rich quick. When the mugger finally makes his move, Reacher rides to the rescue. The old man is grateful, yet he turns down Reacher's offer to help him home. He's vulnerable, scared, and clearly in big, big trouble. Elsewhere in the city, two ruthless rival criminal gangs, one Albanian, the other Ukrainian, are competing for control. Do they have a life-and-death hold on the old guy? Will Reacher sit back and let bad things happen? Or can he twist the situation to everyone's benefit?

"This is a random universe", he says. "Once in a blue moon things turn out just right". The odds are better with Reacher involved. That's for damn sure.