District Crime Squad Inspector SHEUNG SING (Benjamin Yuen), a rising star in the police force, is shot in the head while trying to save a colleague, which changes his entire life. Having a miraculous recovery, he works twice as hard and is dubbed “Hard-boiled cop” but suffers severe sequelae! Chief Superintendent MAN HEI-WAH (Kara Wai) of the Kowloon West Regional Police Headquarters is very ambitious, looking to become the first female Commissioner of Police. The one who shot SHEUNG SING turns out to be YAU BING-GO (Philip Keung), an undercover cop for HEI-WAH. When it comes to investigating cases for HEI-WAH, BING-GO knows no bounds. Yet, in the power struggle against another Chief Superintendent KAN KWOK-CHU (Hui Shiu Hung), HEI-WAH went back on her word, which made BING-GO so furious that he shot at HEI-WAH, but accidentally injured SHEUNG SING. The gunshot incident turns BING-GO into a defector. Shrouded in guilt towards SHEUNG SING, BING-GO secretly helps him solve cases as redemption. Being used as pawns in political power struggles, SHEUNG SING and BING-GO fortunately get helps from Chief Superintendent CHING YU-SUM (Ben Wong) of the Complaints and Internal Investigations office, vowing to end this once and for all……

重案組督察尚垶（袁偉豪飾）原是警隊明日之星，為救同胞，被悍匪在頭部轟了一槍，從此改寫一生。槍傷後奇蹟生還，尚垶查案比以前更拼搏，贏得“鐵探”美譽，不過總日受後遺症折磨！西九龍總區總警司萬曦華（惠英紅飾）野心勃勃，極有望成為警隊首位“一姐”，而槍傷尚垶的，正是曦華的臥底遊秉高（姜皓文飾）。秉高為曦華查案，沒有底線。但曦華為了與總警司簡國曙（許紹雄飾）爭功，竟背棄承諾，秉高一怒之下向曦華開槍，卻誤傷了尚垶。這一槍令秉高成為雙節臥底，更令他對尚垶愧疚不已，於是暗中協助尚垶破案，作為補償。權鬥令尚垶，秉高慘成棋子，幸得投訴及內部調查科總警司程宇森（黃智賢飾）幫助，誓要以權鬥結束權鬥……