Chief Inspector Chen is assigned to investigate a group of environmental activists trying to tackle the pollution issues in China. The case is supposed to be simple, but it is complicated by Chen having history with the leader of the group. Meanwhile Detective Yu is on the trail of a serial murderer.

Inspector Chen is on the case of a serial murderer when he is called away to report on environmentalists trying to tackle the pollution issues in China.

Chief Inspector Chen and Detective Yu Guangming are brought into a serial murder case when the Homicide squad proves incapable of solving it. But before Chen can make a start, he is called away by a high-ranking Party member for a special assignment: to infiltrate a group of environmental activists meeting to discuss the pollution levels in the country and how to prompt the government into action.

Chen knows it will be a far from simple task, especially when he discovers the leader of the group is a woman from his past. Meanwhile, Yu is left to investigate a serial murder case on his own.

Both Chen and Yu face pressure from those above to resolve the cases in a satisfactory way . . . even if that means innocents face the punishment.