An undercover cop Lee Ja Sung infiltrates South Korea’s largest crime organization and spends ten years rising in the ranks. When the head of the organization, Goldmoon, is killed, a conflict of power rise between the successors over the head position. The police interfere too with its plan. Jung Chung, Ja Sung's boss considers him a brother and trusts him a lot. Ja Sung will be torn between his duty as a police officer and fidelity to Jung Chung. (Source: tvN Asia)