C.L.I.F. 4 picks up where the previous season leaves off with the CID team launching a crackdown on the criminal gang that Yang Zhongzheng (Terence Cao) belongs to.
Zhang Guixiang (Elvin Ng), who played a traffic police officer last season, will return to his NPC Community Policing Unit (CPU) as Senior Staff Sergeant and will take his relationship with Weng Xuanmei (Sora Ma) one step further as marriage is on the cards for the couple.