Chief inspector of Hong Kong’s Criminal Intelligence Bureau, Cheuk Hoi, is suspicious of his close colleague’s mysterious death. Adding to the enigma, he discovers that the five undercover agents who were in constant contact with his dead friend have all vanished.

Just an ordinary boy from the Sofia suburbs becomes the first bulgarian undercover cop. Forced by his father when he was young to lie and cheat, Martin becomes the perfect liar. That skill, and also the hatred of the 'underworld' makes him the perfect match for a dangerous mission - to infiltrate the crime organisation of a rich and powerful businessman. While infiltrating and living in fear of being uncovered, Martin falls in love with the most inappropriate woman - Djaro's girlfriend, Suni. Just when he gains the trust of the mobsters, it appears that the real enemy is in the police. Martin is alone against all, facing difficult decisions.

The members of a diverse vigilante group formed to boost the police's image are put in jeopardy when they stumble upon an unexpected drug deal.

When a secret police operation fails, sniper Lee Ho-yeung develops a personal grudge towards his co-worker Ko Chun-kin. Ho-yeung eventually decides to leave the police force and becomes the president of a firearms association, colluding with organized crime on the sky. Through abusing the trust of an unknowing detective and the trust of his girlfriend who still works with the police unit, Ho-yeung has secretly been working against Chun-kin, who has been kept in the dark the whole time. But when Chun-kin starts to suspect the clues within multiple murder cases, a tense standoff between the brothers unfolds.