Daniel, a former police academy classmate, works deep undercover within a criminal gang. By chance, he runs into his old friend Louis, who has been captured. To avoid suspicion, Daniel acts flippant, forces Louis to stay by his side, and feigns intimacy to fool the gang members.
Jack repeatedly plots against Louis, slipping poison and setting deadly traps. Daniel risks everything shielding Louis—even taking poison meant for him. Amid constant mortal danger, quiet romance blooms between the two.
Madam Yu Lian, the ruthless master drug lord, harbors her own schemes, while Jack keeps laying traps to drive a wedge between them. At the fateful banquet, the pair stage a bitter falling-out to mislead their foes. Secretly coordinating with the police, they launch the raid that crushes the entire drug syndicate. At last, the love that crossed the line between cop and criminal can finally be laid bare.