Arthur Bishop is a 'mechanic' - an elite assassin with a strict code requiring professional perfection and total detachment. One of an elite group of assassins, Bishop may be the best in the business - with a unique talent for cleanly eliminating targets. When Harry McKenna, his close friend and mentor, is murdered, Harry's son comes to him with vengeance in his heart and a desire to learn Bishop's trade, signaling the birth of a deadly partnership.

Arthur Bishop is a veteran hit man who, owing to his penchant for making his targets' deaths seem like accidents, thinks himself an artist. It's made him very rich, but as he hits middle age, he's so depressed and lonely that he takes on one of his victim's sons, Steve McKenna, as his apprentice. Arthur puts him through a rigorous training period and brings him on several hits. As Steven improves, Arthur worries that he'll discover who killed his father.