Somewhere in Chile, recently retired assassin Michael Green (Johnny Knoxville) is killed at his stately mansion home by a group of his former work colleagues (Sindy, Facundo, Hilde (Fei Ren), Karl (Robert Maillet) and Alexei) at the behest of Mr. Blut (Matt Lucas), his employer. Sindy acts as the honey trap and the rest of the squad moves in while Sindy distracts the target while having sex with him.Once his employees reach mandatory retirement at fifty, Blut, heavily in debt to his creditors to the tune of $29 million, is forced to pay them millions of dollars in pensions. However, Blut plans to turn this into a profit by murdering them before they reach fifty at which point their pensions will revert to his company, Damocles. The combined pension outgo on Blut's assassins nearing the age of 50, totals to $29 million. Unknown to anyone, Mr. Blut, owner of Damocles, plans to sell the company and is inflating its value by murdering its retired operatives, receiving their retirement benefits by way of a clause in their contract that lists Damocles as a benefactor.Duncan Vizla (Mads Mikkelsen) is fourteen days away from retirement as a working-class assassin and is owed $ 8,207,523.04 upon retirement from Damocles; he plans on settling down in a small suburban town in an undisclosed location. Duncan has many injuries from his past assignments, including a punctured lung and a piece of metal under his chest. His finances are handled by an accountant, and he has multiple properties. He asks his accountant to correspond with him at his Florida address.Duncan is regarded as the most-feared killer-for-hire in the world but is haunted by recurring nightmares of the murder of a family he killed, except for the young daughter who Duncan let go. Known as "The Black Kaiser", Duncan has begun his settlement into relaxation with Camille (Vanessa Hudgens), a young and shy neighbor, and an easily frightened woman. They live in a remote corner of Triple Oak, Montana. As Camile and Duncan become friends, she shares about a traumatic day in her life, brought upon by a single individual whom she hopes to confront one day. One day, after giving an ill-fated talk at a local school about foreign countries and combat (The school asks Duncan never to return as his demonstration was too graphic), he gives Camille a gun as a gift. While trying to teach her how to shoot, she breaks down, seemingly disturbed by the weapon.Blut sends Duncan (via a meeting with Vivian (Katheryn Winnick), Duncan's handler) on a mission to Belarus to kill a target that was supposedly responsible for the murders of the other former assassins. Vivian claims to Duncan that the killings were arranged by the Russian Mafia, who hired some Mexican hit-men to carry out the attacks. The payday promised to Duncan is $1 million. Vivan wants Blut to leave Duncan alone, but Blut is in no position to pay $8 million to Duncan and wants him dead. However, Duncan acts before telling Blut and discovers that he is the true target (when he enters the target's room, he finds his own file photo in his possession). Vivan panics, because now Duncan knows that there was a conspiracy against him, and she was involved.Meanwhile, Blut engaged his A-team to kill Duncan. Facundo's (Anthony Grant) squad works to locate Duncan's residence. While beating his accountant, Lomas (Julian Richings), they receive a list of his current property holdings. They work through the list without any success, killing the various residents of each property. Despite having covered his tracks well, Duncan is tracked down through large donations he has made from a Montana Bank. While coming home from stopping at the nearby town, Duncan finds Sindy (Ruby O. Fee) by the side of her car broken down on the road. The pair return to his house, where they end up having sex. While having sex on the bed, the kill squad engages. Duncan outmatches and kills all of the would-be assassins except for Alexei (Josh Cruddas), who activates "Plan B."Learning from Alexei's girlfriend Junkie Jane, that Camille has been kidnapped by Alexei, Duncan goes to Detroit to meet with former mentor, Porter (Richard Dreyfuss) only to be betrayed and drugged by him before learning any information.Duncan is tortured for three days by Blut, losing his left eye and other bits of flesh in the process. Overnight, Duncan uses the broken blade to pick the locks on his shackles and, by morning, escapes the mansion, killing many of Blut's henchmen. Duncan goes to an old lover, Jasmine (Ayisha Issa), for help, healing, and weaponry.Vivian, another former lover and Duncan's old handler, leads a task force to ambush Duncan when he offers to trade himself for Camille, but Duncan takes out the entire task force using Jasmine's remote-controlled machine guns. Blut's remaining men desert him rather than face Duncan's wrath, and Duncan decapitates Blut in retaliation for his actions.Discovering the heavily drugged Camille, he returns to Montana, where he treats her inside her cabin. Duncan awakens the following morning to find her gone. Searching her room, he finds newspaper clippings from twenty years prior about the death of the family he has nightmares about murdering and $200,000 check stubs.Camille reveals herself to be the young daughter of the family who had been spared by Duncan and who he has been financially providing for from a distance ever since. Haunted by the murders, Camille had tracked Duncan down for revenge. Though Camille tries, she is unable to bring herself to kill Duncan. Duncan promises to help Camille try to find out who had put a hit out on her father.