Detective Zuo Luo, a police officer who lives by his principles, watches his life collapse in a single rainy night. His moral choice to save a stranger on the street—rather than arriving on time to rescue his partner, Liu Mo—results in Liu Mo’s death at the hands of an anonymous mastermind on a hotel rooftop. Three months after the release of several detainees Liu Mo had arrested using illegal force—and the subsequent disbandment of the Special Serious Crime Unit 7 (SSCU-7)—Zuo Luo returns to lead the tainted Group 7. Under “Project Retrogade Mercury,” he is forced to recruit his new special consultant: Su Cheng. Su Cheng is a brilliant, mixed-race private detective suspected of laundering money for a high-level international syndicate. He also knows about the “Ghost Gang”—the most elite, undetectable criminal organization in the world. To avenge his partner’s death and clear his own name, the rigid Zuo Luo must work alongside the cunning, amoral Su Cheng. Together, they must hunt ghosts within a ruthless criminal underworld—proving that Zuo Luo’s troubles have only just begun.