Jack Reacher breaks a bully's nose and finger after being repeatedly provoked in a Texas saloon, so when the bully turns out to be a local sheriff and shows up with three of his colleagues the following day to arrest him, Reacher decides it's time to move on. He chooses hitchiking as the fastest escape and hooks up with a driver of Mexican heritage named Carmen Greer. She says that the only reason she stopped, however, is because she has a problem, a really big problem. Her tax-evading husband, Sloop, is coming out of prison soon, and he will inevitably continue beating her as he did so many, many times before. Carmen has been diligently searching for candidates to kill him, and she thinks Reacher's military background may qualify him for the job. Reacher initially refuses and even leaps out of the car and back into the sweltering 110-degree (Fahrenheit) heat, but then he expeditiously changes his mind and agrees to accept a ride back to the ranch. It is there that Carmen, her husband Sloop and the rest of his family live, and Reacher is promising nothing more than to look into the situation and, if necessary, to act as her bodyguard. Carmen and Jack then proceed to pick up her daughter Ellie who gets on well with Reacher.
During this time we also see the introduction of two hired threesomes of people: the first group, named "The Watchers", is composed of two men and a boy and has been keeping a vigil over the ranch where the Greers live. This trio is later terminated without pay by a group of stone-cold assassins called "The Killing Team" who have previously done away with Sloop's defence lawyer Al Eugene.
Carmen and Reacher arrive back at the ranch, but Jack does not receive a warm welcome from Sloop's mother, brother or the two ranchers who work there. Nonetheless, Reacher manages to get himself hired on as a horse wrangler. In the days leading up to Sloop's release, Jack teaches Carmen how to fire a pistol and falls into a fracas with the aforementioned hired hands. Sloop comes home and takes a dislike to Jack, and he eventually gets the Texas Rangers to take Reacher away.
The Rangers bundle Jack into their cruiser with intentions of letting him out in Pecos, but the troopers are called back to the Greer Ranch, or the "Red House", whilst Reacher is still in the car. Sloop has been shot and killed, and the authorities think it was Carmen. While she is incarcerated, furthermore, she suddenly confesses to the murder and assiduously denies legal help from Alice Amanda Aaron, the pro bono attorney whom Reacher procures for her.
Alice and Jack, nevertheless, are convinced of Carmen's innocence and stubbornly continue trying to prove it, despite the presumably credible and damaging claims of Hack Walker. But as this character is the self-serving Pecos County's district attorney as well as Sloop's oldest friend, the investigative twosome remains unconvinced of his allegations. Complications (like Ellie's kidnapping) and backstories (like wasted teenage years) abound, and there are deceptions within deceptions which muddy the waters enough to keep the reader guessing throughout most of the multiple storylines.