Lee Child's latest novel featuring the exploits of Jack Reacher. As usual, what Child does looks easy, but it's not: if it were, more people would be doing it.
As often happens to Reacher, he just falls into the plot due to his powers of observation and deduction. In this case, riding an intercity bus, he notices an old guy with an envelope of money sticking out of his pocket. But Reacher also notices a different guy noticing the same thing. Suspecting an imminent mugging, Reacher gets off the bus with the old guy and—yup, prevents the crime.
But why is the old guy carrying around all that cash? Reacher gets sucked into his predicament, which is owing a bunch of money to a mob-connected loan shark. Which, it turns out, is just the frosting on a bigger problem. And just to make things more interesting, all this happens in a city where two mobs, one Albanian, the other Ukrainian, just happen to be starting a war for each others turf.
Unsurprisingly, because it's Reacher, things escalate into a three-way war between the mobs and Jack. This turns out to be a bad career move for the mobsters.