Lonely City, a flashy but decadent city of sin, is full of competition for money and interests. However, in this paradise of desperate criminals, there are still a few people who insist on justice in their hearts... Under the planning of his superior Azan, police undercover Yu Qiu has successfully infiltrated local gangs many times and mediated among various black forces. Yu Qiu seems to have gradually lost himself in the life of the gangsters. He began to doubt whether only "extraordinary" means can be used to uphold justice, which made Azan begin to question it. In an undercover operation, Yu Qiu risked the failure of the operation and fought fiercely with the gang boss, but all of them died on the spot. Under the dual questioning of morality and underworld morality, Yu Qiu chose self-exile and fled from Lonely City. However, Yu Qiu's inner desire to punish sin has never diminished. He regrouped and returned to Lonely City. This time, Azan gave him the task of investigating the most evil and mysterious black hand behind the city of sin, the leader that everyone fears - "the boss". Starting from a bizarre kidnapping case of a child, Yu Qiu and Azan found out the identity of the boss and the criminal network behind him. The mysterious boss controls the business world and the underworld. Only by destroying the boss can this fallen city be saved. In fact, Yu Qiu has stepped into the traps set by the boss during the investigation. Although Azan desperately defends the bottom line of the law, the boss's power has infiltrated the top level of police power. Yu Qiu gradually loses support, and the child he was supposed to protect is also threatened with his life. In the ensuing puzzles, Yu Qiu, who insists on justice, seems to be pushed into deeper despair...