Unable to satisfy his sexual desires with his wife, Biu regularly visits prostitutes. Afterwards, he ties up and tortures them in various ways before killing them. Biu believes that if they die, they will be reincarnated and have a better life. He murders over a dozen people. One day, a young woman named Yuk comes to stay with Biu's family. He falls in love with her but is afraid that he will kill her, so he makes her leave. Yuk has nowhere to go and starts working as a prostitute. When Biu finds her doing this, he has sex with Yuk and gets her pregnant.
Unfortunately the movie Diary of a Serial Killer is not yet available on HBO Max.
| Directing | Norman Chan | Director |
| Sound | Yau Ning Wong | Sound Effects Editor |
| Crew | Cheung Man-Po | Cinematography |
| Editing | Angie Lam On-Yee | Editor |
| Writing | Philip Cheng Chung-Tai | Writer |
