Eun Dae Gu, Eo Su Seon, Park Tae Il, and Ji Guk—nicknamed the P4—are rookie detectives in Gangnam’s violent crime unit. Each joins the team for different, often questionable reasons, and none seem cut out for the job. Leading them is the fiery Seo Pan Seok, who wants nothing more than to be rid of them. But as cases unfold, unexpected growth and teamwork begin to surface.