We soon find out the bad guy who is controlling everything is called The Zec ('The Prisoner') who has survived a number of years in concentration camps, and had to chew off his own fingers to stop frostbite in his younger days.
In a series of flashbacks, we see that his right-hand man, Charlie, was behind the shooting and they framed Barr for the murders.
Reacher is intrigued about the fact that Barr messed up so blatantly by paying for the parking meter, and that his den was too perfect as an evidence-backed crime scene.
A local rat hired by The Zec to follow Reacher uses his own initiative to hire a local gang to beat up Reacher, which doesn't go to plan. Charlie kills the informant, and then is sent to clean up the mess with his Russian friend Vlad.
Reacher follows a hunch to find Sandy (the honey trap), and confronts her at the Auto Part shop. She gives him the keys to their leader Jeb's car, and Reacher sets off to his home. His mother alerts his friends who smack him over the head with a baseball bat, but Reacher comes good and beats them up. Again.
Charlie is waiting outside. Reacher then goes to see Helen to keep her informed of the investigation, and they run a trace on the Russian car following them. They soon enough crack the case - the person behind the shooting is someone who has an interest in the widow's business, who was the second to be shot - and the one the shooter took time over. The person who had his business offer rebuffed was a Russian -- The Zec.
Taking things to the next level, Charlie murders Sandy to tie up another loose end, and frames Reacher for it. Emerson and the cops show up at his motel, and start the big car chase you'll have seen in the TV spots. Reacher gets away by jumping out and taking the bus instead.
Reacher finds a gun-range just far enough away to account for Barr's petrol expenses at weekends, and confronts Cash (Duvall), the owner. They go over surveillance footage to see that Barr had a friend -- Charlie, who practised on the range but switched the targets to give Barr the credit and kudos as the best sniper around.
Reacher calls Helen to warn her that he has been double-crossed since the beginning - and the only ones who knew about him where Helen, Rodin (the DA and her father) and Emerson. She confronts her father and believes it's him -- until she gets into the lift and is tazered by Emerson. She is taken hostage and held to bring in Reacher.
Reacher doesn't take the bait and enrages Charlie. But he calls back and agrees to meet them for a showdown.
Cue the 1980s Schwarzenegger/Stallone type gunfight at a dis-used quarry. Reacher brings in Cash to lend a hand. Reacher drives Helen's car closer to the action, while Cash fires at the bad guys from up high. Slowly he takes out the henchmen, before Reacher gets the drop on Charlie.
To show he is an honourable guy, he throws away his weapon and they fight. Reacher breaks his enemy's leg, and still wins.
Emerson and The Zec are the only bad guys left. I forget what happens to Emerson (does he kills himself?), but then Reacher walks into the main hut, frees Helen and then takes out The Zec with a bullet to the head.
He's off before the cops show to fight crime another day.