Eun Dae-Gu, Eo Su-Seon, Park Tae-Il, and Ji Guk—known as the P4—are fresh recruits thrown into the intense world of Gangnam’s violent crime unit. None of them are exactly thrilled or ready for the challenges ahead; each joined the force for their own, often shaky reasons. Their leader, Seo Pan-Seok, is a hot-headed veteran who’s more interested in ditching these rookies than mentoring them. But as the P4 stumble through their cases, make mistakes, and even find unexpected romance, they begin to grow into the officers their city desperately needs. Chasing justice on the streets, the four flawed cops learn how to trust themselves and each other.