Arthur Bishop is a methodical, emotionless hitman who works for a secret organization. His assignments involve meticulous planning and precise execution, ensuring that each kill looks like an accident or a natural death. Bishop lives in a luxurious home and leads an isolated, solitary life, adhering to a strict code of professionalism. His only connection to the world is through his long-time friend and mentor, Harry McKenna, who also serves as a liaison to the organization. When Bishop is assigned to eliminate McKenna due to a supposed betrayal, he reluctantly completes the task, though it leaves him conflicted.

Afterward, Arthur forms an unlikely partnership with Harry's disenfranchised son, Steve. Steve, fascinated by Bishop’s profession and adept at handling dangerous situations, persuades Arthur to train him in the art of assassination. The duo embarks on a series of jobs together, but Steve's reckless behavior and impulsive nature often contrast sharply with Bishop’s meticulous approach. Tensions begin to rise as Steve’s unpredictability threatens to dismantle Bishop’s carefully controlled world, leading to unforeseen consequences that test their loyalty and survival skills.