After graduating from the police academy and being commissioned as a lieutenant, Ji-yong investigates the suspicious complainant Hwang Seong-gu and encounters a nationwide rental scam case. As Ji-yong pursues the rental scam gang that evades proper legal judgment, he feels his vigilante rules being tested. While chasing the rental scam gang, the four vigilantes receive threats from someone aware of their identities. They begin to sense the shadow of a great evil from their adversaries.