“What the hell do you think you’re doing to your own family, you bastard?” Kim Eun-ho, a rookie cop, goes undercover inside the contract-killing organization Eden Company. By a stroke of luck, he survives by becoming the direct junior of the syndicate’s ace killer, Tae-i. Recognizing Eun-ho’s hidden talent, Tae-i begins training him as a professional assassin. The two complete opposites slowly grow closer, forming a bond like brothers. But as Eun-ho sinks deeper into the organization, caught between being a police officer and a killer, he begins to lose his sense of who he really is.