Line Walker

Chief Inspector Cheuk Hoi of Hong Kong's Criminal Intelligence Bureau runs five undercover agents planted inside a major triad organization. When a fellow superintendent is killed, it comes out that the files identifying those agents have been deleted from official records, and Cheuk Hoi has to work out which of the people around him he is still responsible for protecting before the corrupt officer behind it all does.

The agents, including Ding Siu-ka and Sit Ka-keung, keep infiltrating the triad while suspecting that their own handler could be the mole, with an ICAC investigator and a prosecutor working the case from the outside as the triad leader Chum Foon-hei tightens his grip.

Line Walker starred Michael Miu, Charmaine Sheh, and Raymond Lam, with Sharon Chan, Benz Hui, Sammy Sum, and Elena Kong in supporting roles. The 31-episode series aired on TVB Jade in 2014 and became the biggest Hong Kong drama of its year, putting the undercover format, already a local speciality, back at the center of the schedule.