Wesley Gibson (JAMES McAVOY) is a timid man who works as an account manager for a mean boss, Janice (LORNA SCOTT), and whose girlfriend, Cathy (KRISTEN HAGER), is having an affair with his friend and coworker, Barry (CHRIS PRATT). Thus, he's shocked when he finds himself the apparent target of Cross (THOMAS KRETSCHMANN), an assassin who reportedly just killed Wesley's long lost father, also an assassin.
So says Fox (ANGELINA JOLIE), yet another assassin ultra handy with firearms and fancy driving who arrives just in time to save Wesley from Cross. When she takes him to see their leader, Sloan (MORGAN FREEMAN), Wesley learns that they belong to a secret organization of assassins known as The Fraternity. Formed 1,000 years ago by a group of weavers, they carry out their target orders not only with precision, but also the ability to overcome various laws of physics, including being able to bend the trajectory of their bullets.
Wesley thinks this is all nonsense, but soon discovers that he too possesses such an ability. Following some brutal training at the hands of Fox as well as other assassins including The Gunsmith (COMMON), The Repairman (MARC WARREN), The Exterminator (KONSTANTIN KHABENSKY) and The Butcher (DATO BAKHTADZE), Wesley is inducted into The Fraternity and sets out on his first mission.
Yet, the person he most wants is Cross who he's told is a rogue assassin who left their organization. Tracking down his arms supplier, Pekwarsky (TERENCE STAMP), Wesley then sets out to find and kill Cross, unaware of developments that will rock his new world.