When he was younger, Hugo Ng accepted a mission to infiltrate the triads as an undercover agent. The triad leader's daughter, Christine Ng, fell in love with him at first sight. Although Hugo already had his heart set on the simple Mimi Kung, he pretended to be with Christine in order to solve the case. As a result, he quickly rose through the ranks in the triad. One time, during a fight between triads, Hugo eliminated Christine's triad rivals, but Christine's fate remained unclear. Hugo's good friend, Michael Miu, knows about his affair with Christine and their infant son (Bosco Wong). Hugo brings Bosco home and Mimi also gives birth to a son (Ron Ng). Because of the sin that he represented, Bosco did not grow up with love from his father. But Ron also did not get spoiled by Hugo and instead had to go through many hardships. The half-brothers accumulate a number of grudges growing up. Each of them also coincidentally develop a father-like mentor relationship with Michael. During a grand promotional ceremony, Hugo, having achieved the rank of Superintendent, is happily preparing to receive this honour, but unknowingly steps into a revenge plot that is thirty years in the making...