After they depart, law enforcement is notified that Joe Schitt (villain in Book I) and another criminal have escaped from prison. They are hunting Barlow and Sarah to kill them in revenge for Joe Schitt's arrest and incarceration. (The fugitives have the rough itinerary of the honeymoon from the wedding announcement in the newspaper.)
A deputy from Quayle County is dispatched to try to find and warn Sarah and Barlow because they haven't been in touch with Sarah's parents, and their exact whereabouts are unknown. It's a race against time in a lethal game of cat and mouse.