Lea is a rookie cop and former partner to Youngjae, who went undercover to infiltrate the ranks of the notorious gang, BAP. However, when she is caught in public with him, she is forced to pretend to be his sister, and is dragged into a world of luxury and crime. What nobody knows is that she has her own personal vendetta against BAP, and would like nothing more than to see the lot of them rotting behind bars. What happens when her own personal feelings interfere with her sense of justice?