NOTE: This spoiler was sent in by Marcus.

The film begins in Ethiopia, where sniper Bobby Lee Swagger (Mark Wahlberg) and his scout Donny Fenn (Lane Garrison) lay in wait in the hills. Their mission is to cover American soldiers as they head back to base. They pass the time with some small talk, and Donny looks at a photo of his wife, Sarah (Kate Mara). A truck drives towards the American convoy with a soldier manning a machine gun in the back. Swagger blasts the shooter through the head, along with the driver. It seems like the mission is over as the Americans make their way through the road, but then a horde of hostiles appear and fire at the soldiers. The Americans make it out while Donny instructs Swagger who/where to shoot, killing numerous people. The enemy force fires upon the hill, trying to kill the snipers. Back at base, their commanding officer makes everyone shut down the operation, since the Americans aren’t supposed to be in the country. This leaves Swagger and Donny to fend for themselves without any support. A helicopter comes around and blows Donny’s stomach open with its machine guns, killing him. Swagger fires upon the helicopter, eventually causing enough damage for it to crash and explode.
36 months later – Swagger is seen in the mountains, unshaven and with long hair. He lives alone; his only companion is his dog. He goes inside his cabin, where his dog opens the fridge and takes out a cold beer for him. Swagger lets the dog drink some and goes on the internet to look at news. Meanwhile we see wheelchair-bound Michael Sandor (Rade Serbedzija) approaching Colonel Isaac Johnson (Danny Glover), Jack Payne (Elias Koteas), and Louis Dobbler (Jonathan Walker) in an office. Sandor recommends Swagger for a job, and the men discuss Swagger’s past. Shortly afterwards, Johnson and his men drive out to the woods to meet him. Swagger’s dog barks when it sees the truck, and Swagger is alerted before they get to his cabin. Johnson introduces himself to Swagger, and shows him his medal of honor. He wants to talk to him, but Swagger is not interested. Payne tries to lure his dog to him, but Swagger warns him not to shoot his dog. Payne slowly reaches for his gun as Swagger readies a hidden blade. Johnson calms both down and convinces Swagger to give him five minutes. Payne and Dobbler wait outside as Johnson explains their presence – they have received information that someone is going to try to assassinate the president. There is a mole in one of their agencies, which is why they are trying to get outside help. The intel they got explicitly states that the shot will be taken from beyond a mile, a shot which only a few men can do. Swagger doesn’t care and wants nothing to do with it, but Johnson insists that he helps plan the assassination, since he knows what to look for (and his knowledge can help them find the shooter). The president will travel to three different cities, and Johnson wants Swagger to travel to each and scout potential places for a sniper. Before Johnson leaves, Swagger admires his truck’s engine and takes a picture of it. On their way back, Johnson and his men fully know that he didn’t take a picture of the engine, but of their license plate.
Swagger sets up a can of beef stew and practices the beyond a mile shot, nailing it with complete accuracy. Next, he cleans his guns and tells his dog that he’ll be gone for a couple of days. Swagger cuts his hair and trims his beard, then goes to each location and scouts out each area. When he’s done, he reports to Johnson that the assassination will highly likely take place in Philadelphia. Johnson wants Swagger there to help catch the shooter. The day of the speech comes, and all authorities get into position. Snipers are everywhere, along with federal agents including Nick Memphis (Michael Pena). Swagger is in a building with Johnson, Payne, and Dobbler. The shooter is possibly in a church tower nearby, and Johnson says that they will take him down just after the president begins to speak. Payne introduces pudgy police officer Timmons (Alan C. Peterson), and Swagger immediately recognizes that his gun is not properly holstered. The Arch Bishop of Ethiopia is accepting an award, and the president will speak afterwards. As the president approaches the stand, Swagger urges Johnson to have his men take down the shooter immediately. The Ethiopian Arch Bishop is shot in the head. Swagger is shot in the shoulder by Timmons and falls out of a window, landing hard on the glass ceiling of the section below. Timmons then shoots Swagger in the stomach, causing him to fall through the glass ceiling. Payne gets pissed at Timmons for not killing him while Johnson and his men pack up their things, leaving only Swagger’s sniper rifle along with a bullet. Payne orders Timmons to finish Swagger off.
Swagger runs into Memphis and asks for his help. Memphis draws his gun on him, and Swagger flips him over hard on the ground. He handcuffs him to a gate, and tells him that he was set up and Timmons is in on it. Swagger grabs his gun and steals his car. Timmons catches up to Memphis, and alerts the cops that Swagger stole an FBI car. Now everyone is searching for Swagger, and he drives into a car wash to hide from the helicopters. While his car is being washed, Swagger hops in the back seat and cuts a hole to the trunk, where he grabs a medic kit and tends to his wounds. When he’s finished, he speeds out of the car wash and is seen again by the cops. The back end of his car is smashed by a truck, causing him to spin around until he’s directly in front of a line of police officers. He puts the car into reverse as the cops open fire on him. Swagger drives through a construction site and directly into a lake. The cops find the car, but no Swagger. He is pulled alongside a boat, and makes it underneath a bridge. From there, he hotwires a truck and takes off. Meanwhile, FBI agents watch a news report of the assassination attempt and of Swagger’s escape. They all are not happy that Swagger overpowered Memphis so easily, even though Swagger is highly trained and Memphis is three weeks out of the academy. While meeting with his superior officer and other agents, Memphis tells them what Swagger said to him, but they all say that he didn’t hear anything. Memphis will be put up for review. Swagger drives to a store and knocks out the power, then goes inside and buys supplies. Swagger drives to an empty car repair station and makes an IV for himself using the supplies.
Swagger drives all night to Kentucky, where he goes to Sarah’s home. She’s startled by him coming by, since she’s seen the news about what happened. Sarah lets him come inside, and he apologizes for not coming to meet her after Donny died. She did receive his letter though, along with flowers each year on the anniversary of Donny’s death. Swagger gives Sarah a list of things to get, and sends her out to get them. She eventually buys everything, and he quickly instructs her how to treat his bullet wounds before passing out. Even though she’s not a nurse, she does a decent job of cleaning him up. Meanwhile, Memphis looks further into the assassination attempt and discusses it with FBI agent Alourdes Galindo (Rhona Mitra), who tells him to stop looking into it. The facts don’t add up though, since there are several discrepancies with the news and Timmons’ story. He wants to talk with Timmons about it, but it turns out he was murdered the previous night in a "botched burglary". Memphis goes to all of the locations that Swagger went to, and goes to the church tower where he sees specific markings in the dust. He’s convinced that Swagger isn’t the guy they should be after, since he would not have missed the president and hit the Ethiopian Arch Bishop. Memphis also goes online to a gun chatroom, where he finds out exactly what kind of gun was used in the assassination attempt. During this time, he begins to notice that people are watching him.
Swagger eventually gets better, and tells Sarah that he’s going to go after the guys who set him up. Sarah informs him that news reports are saying that Swagger killed his dog and tried to kill the president, with pictures released of him scouting out each location. Swagger is pissed that they killed his dog and plans to see this through to the end. He blames himself for Donny’s death, but Sarah slaps him in the face and tells him that Donny fully knew what he got into. Sarah gives Swagger Donny’s first sniper rifle and volunteers to help him. Their first course of action is to find Memphis. Sarah wears a disguise and meets Memphis in a public place, handing him the photographs of Johnson’s license plate. Swagger watches across the street, but is seen by police who think that he’s suspicious. Two cops approach him, one with an attack dog. After Sarah and Memphis leave, Swagger throws coffee into a cop’s face and makes the dog attack the cop. He then throws the cop and dog through a window while beating the crap out of the other police officer. He ditches his jacket and walks away. Memphis sneaks into a restricted area of the FBI office and tries to find information about the license plate number, but he’s blocked out and requires a delta level clearance. Galindo tells him that he’s going to be fired if he keeps looking into this, and starts to notice the faults as well in the “facts” of the Philadelphia shooting. She winds up telling him how to get the security clearance though. Dobbler informs Johnson about the internet chatroom, and someone trying to access delta level security information. They realize that Memphis is looking where he shouldn’t, and plan to take him out.
As Memphis is walking on a bridge, he is abducted by masked men in a van. Memphis is severely beaten, and the men put him in a rig that will make him shoot himself. Swagger shoots each man one by one using Donny’s rifle, and frees Memphis, who knows that Swagger was set up and agrees to help him. Johnson hears that Memphis didn’t die and knows that he’s now working with Swagger. He orders his men to look deep into Swagger’s past. Memphis drives them to Tennessee, where they visit an old humorous marksman expert. Swagger asks the expert who could make a shot beyond a mile that’s still alive. Apart from Swagger, there’s one man. The sniper used to be sadistic, just shooting to wound and killing everyone who tried to help the wounded. He must’ve killed hundreds of people. He was in a building that was destroyed, and some believed him to be dead. The sniper is Michael Sandor, the handicapped Russian that’s working with Johnson. Johnson knows that Swagger is going to look for the shooter, and so lets Sandor act as bait to lure Swagger out. Dobbler found that Swagger has sent flowers to Sarah each year, and believes that she helped him. Johnson orders them to get her.
Swagger and Memphis go to a big hardware store and buy lots of supplies. They then drive out to the woods where they make napalm, pipe-bombs, and gas bombs. Swagger teaches Memphis to use a sniper rifle, and makes him practice while he sets off bombs nearby. Meanwhile, Sarah thinks that someone’s in her house and takes out her shotgun. A henchman appears with a silenced pistol, but is blasted through the chest by Sarah. Payne sneaks up behind Sarah and makes her put down the shotgun. He asks her where Swagger is, and beats her up. It’s heavily implied that Payne rapes Sarah. Elsewhere, Johnson meets with corrupt senator Charles Meachum (Ned Beatty) and gets his approval to fly in over twenty soldiers to kill Swagger.
Swagger and Memphis find where Sandor is, and plan an attack. Memphis remains in position near the forest while Swagger moves closer to the cabin. He sneaks up behind a guard and stabs him in the back, then sets up some bombs. He stabs another guard through the chin, and again places more bombs. Swagger makes quick work of the third guard, and shoots the fourth in the head. Sandor is all alone now, and reveals to Swagger what really happened. The president was never in any danger – their only target that day was the Ethiopian Arch Bishop, because he was going to talk about Americans committing genocide to build an oil pipeline (approved by our government, since nothing happens without their approval). The best way to kill the Arch Bishop was to make it look like a failed attempt on the president. Swagger unwittingly was part of the genocide, since back in Ethiopia Donny and him were covering the soldiers that murdered the villagers. Swagger asks about Johnson, but Sandor doesn’t know what his real name is, though he does know that he works for Meachum. Soldiers surround the cabin, and Memphis warns Swagger. Sandor pulls out a pistol and shoots himself in the head. Swagger orders Memphis to set off the pipe-bombs, and then the gas bombs. Two soldiers come into the house, and Swagger shoots both dead. Memphis sets off the bombs, and Swagger shoots his way out of the cabin. Memphis covers Swagger, and a big shootout ensues. Swagger makes it to Memphis, and a helicopter shows up to kill them. Swagger thinks back to Donny’s death, and fires upon the helicopter. Both men run a safe distance and set off the napalm bombs, blowing up the remaining soldiers and destroying the helicopter. The incident is covered up though, since all the bodies were removed before the authorities showed up.
Memphis calls the FBI field office and talks to his superior officer, informing him that he has Swagger in custody. He talks long enough for them to trace the call. Swagger then calls Johnson, who tells him that he wants to meet. Johnson reveals that he has Sarah, and Swagger reveals that he recorded Sandor’s confession about everything. Johnson agrees to meet, but wants to see him coming from a long way off. Swagger requests that Meachum be present. The meeting is in the snowy mountains where Johnson, Meachum, Payne, and Sarah are present. Payne rigged a shotgun to his hand and is holding Sarah at gunpoint. They see Swagger walking towards them in the distance, and he is immediately shot in the chest by a hidden sniper. Johnson and Meachum are pleased, but their hidden snipers are shot through the head one by one. Turns out Swagger was posing as a hidden sniper while Memphis was walking towards Johnson. Memphis pulls out his armor and continues to walk towards them. Swagger aims carefully, and destroys Payne’s shotgun while blowing off his thumb. Payne laughs in shock, and then Swagger blows off his arm. Memphis disarms Johnson and Meachum, and Swagger finally approaches them. Sarah grabs a pistol and shoots Payne to death. Meachum offers Swagger a job, but he refuses. Memphis calls in the FBI to come to their location, and Swagger burns Sandor’s recording. Memphis tells him that it proves he’s innocent, but Swagger knows that whoever turns over the recording is dead. No one there is innocent, and so they wait for the FBI to show up.
Some time passes, and Swagger is brought to a meeting in the Department of Justice. Present are the attorney general, Johnson, Memphis, and Sarah. Memphis shakes Swagger’s hand and hands him something. In front of him is his sniper rifle, and Swagger’s hands are freed. He asks if the rifle has been tampered with by the FBI or any other authority, but it hasn’t. He asks Memphis if he believes he’s innocent, and if he trusts him with his life. Memphis answers yes, and Swagger loads a bullet into the rifle. He aims for Memphis, and pulls the trigger. Nothing happens. There’s no way he could have killed the Ethiopian Arch Bishop, since before he left to scout locations he removed all the firing pins from his weapons (including the rifle in front of him that was supposedly used in the shooting). Swagger and Memphis try to pin the mass grave in Ethiopia to Johnson, but it’s not an international court and the attorney general has no jurisdiction over crimes Johnson may or may not have committed in other countries. Johnson is allowed to leave, but not before he tells Swagger that he won again. The attorney general frees Swagger, convinced that he’s innocent.
Later that night, Johnson celebrates his victory with Meachum and Dobbler in a cabin. Meachum and Johnson laugh about winning again, and Meachum plans to move Johnson out of the country to fix another problem they have. As Dobbler begins to explain his next mission, blood splatters on his face. A dead guard falls down directly in front of him. Johnson realizes that Swagger is there, but is shot through the chest. He dies very painfully. Dobbler turns off the lights, and Meachum orders him to get the car. Meachum’s SUV explodes, and the men panic. Swagger moves below the cabin, and Dobbler tells the remaining guard that he’s under the floor. Swagger shoots Dobbler through the knee, and shoots the guard to death from below. He then enters the cabin, where Dobbler pleads that he spares him since he didn’t do anything. Swagger shoots Dobbler in the chest and approaches Meachum. He says that he’s a senator, and he can’t do this. Swagger blows his brains out with a pistol and places it in Johnson’s hands. He breaks the gas line of the cabin and it explodes as he walks away. Swagger runs off to a car with Sarah behind the wheel, and the film ends with them driving off.

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Mark Wahlberg is captured in the end, and reveals that his he removed all of the firing pins from his guns before he left for the mission, and thus the gun allegedly used to kill the Arch Bishop was unusable at the time of the murder. He is freed and enacts revenge by staging Glover's suicide and making it look like Glover killed the Senator he works for.