Line Walker (2016) on Netflix

Plot summary

Inspector Q and Police Constable Ding Siu-ka are senior members of the CIB, the unit on the trail of a drug ring that has grown across the city. An unexpected message arrives from Blackjack, an undercover agent who has gone missing, and the CIB sets out to reach him before it is too late. Tung Pak-ho, the paranoid head of the drug mafia, turns his own crew against each other, suspecting a mole among them. Boss Blue and Shiu Chi-long, his right-hand man, each want to come out on top of their outfit, a contest that plays out despite the friendship between them.