Three years ago, police officer Liu Yuanwen sends back wrong intelligence, seemingly causing the death of his fiancée and fellow police officer Rong Yu. He also loses a friend in Rong Yao , his brother-in-law-to-be and member of the drug task force. Disheartened by all the events, Liu Yuanwen resigns from his position and cuts off all . In the present time, Rong Yao has been promoted to leader of the task force, and is ordered to provide ongoing and resources to the sole undercover operative in Group K, a drug cartel led by the ‘Spectre’ Mr. Ou. Turns out the undercover Mu Qing is actually Liu Yuanwen, and the pair must work together to bring the criminals to justice.