Law with Two Phases (1984)

Chief B (Danny Lee) is an unconventional CID member who relies more on instincts rather than by the book to resolve situations. He's a down-to-earth fellow who's a mamma's boy, not too well-educated, and an outstanding member of the CID. Police Officer Kit (Eddie Chan) has just been promoted from the rank-and-file to CID, and at the same time is studying for the test to become an Inspector. Chief B takes him under his wings to investigate numerous gang-related cases. Kit, previously a by-the-book type of police officer, learns a lot from Chief B.

Unfortunately the movie Law with Two Phases is not yet available on HBO Max.