A killer called "Darker" has been leaving a death notification card after killing scumbags who evaded the law. Police reacted by forming a task force with the elite personnels from each field to capture the vigilante. But in reality, what each department did was dumping their best but most eccentric members to the task force. There is the high IQ but low EQ criminalist Luo Fei, the ill-mannered profiler Mu Jian Yun, the inflexible captain Han Hao, the cowardly crime lab specialist Yin Jian, the gothic loving forensic pathologist Liang Yin, the hacker Zeng Ri Hua, and the volatile combat specialist Xiong Yuan. With each murder, the task force uncovers the crimes the victims had committed, at the same time, gets closer to finding the mysterious vigilante.

The special task force is adrift after their epic loss to Darker, the mastermind behind series of high profile vigilante killings. With their captain on the run for murder and them no closer to catching Darker, the team switches gear and investigates a decades-old hostage case. In those dusty old files, they discover Darker's real identity and a possible police coverup, but establishing the wrongdoer and the aggrieved party proven more difficult than it seemed. The team must determine the true culprit before Darker does, lest he kills his way through the suspect list.