Wesley Gibson starts out as your typical office drone, he suffers from panic attacks and hypochondria, but everything changes the day that he finds out that his recently-assassinated father was a member of an ancient fraternity of assassins.
Wesley has inherited his father's gift of perfect aim and uncanny skill with any weapon. When under stress, Wesley's heart beats in excess of 400 beats per minute, sending abundant amounts of adrenaline into the bloodstream. This allows Wesley to see and react faster than normal. He can also curve bullets.
Fox, a member of the fraternity, tests Wesley by making him shoot the wings off of flies. Wesley refuses at first, but when a gun is put to his head, triggering a panic attack. Wesley actually manages to do it, much to his own surprise.
The next day Wesley wakes up hoping that everything was a dream, but discovers a gun which he had stashed in a toilet tank earlier on, and that he has $3.6 million dollars in his bank account. He quits his job and joins the fraternity, living a life as an assassin.