| Cast overview, first billed only: | |||
| Tony Chiu-Wai Leung | ... | Chan Wing Yan (as Tony Leung) | |
| Andy Lau | ... | Inspector Lau Kin Ming | |
| Leon Lai | ... | SP Yeung Kam Wing | |
| Daoming Chen | ... | Inspector Shen Chen (as Chen Dao Ming) | |
| Kelly Chen | ... | Dr. Lee Sum Yee | |
| Anthony Chau-Sang Wong | ... | SP Wong Chi Shing (as Anthony Wong) | |
| Eric Tsang | ... | Hon Sam | |
| Sammi Cheng | ... | Mary | |
| Carina Lau | ... | Mary Hon | |
| Edison Chen | ... | Young Lau Kin Ming | |
| Shawn Yue | ... | Young Chan Wing Yan | |
| Chapman To | ... | Tsui Wai-keung | |
| Waise Lee | ... | Chan Chun (as Lee Chi Hung) | |
| Ka Tung Lam | ... | Inspector Billy | |
| Ting Yip Ng | ... | Inspector Cheung | |
Because Chan was being expelled from the school in 1991, SP Yeung Kam Wing graduated, with all police reports distinctions, being the first in whole class. Twelve year later, he was being sent, working to Lau. Ten months after Chan dies, Yeung's spy had blew a case and the spy wish to kill Yeung, but Yeung took his gun and shot him to conclude this failure. Lau gave Yeung car park seat B3A6 when Yeung met Lau. Yeung asked Chan who he is, but Chan didn't remember him. Sam works with Yeung and Lau is recording Yeung's words so that he can sue Yeung. Yeung is a police SP, which is being sent to Sam as the spy from police. Lau doesn't really know Yeung's Police SP position and wish to catch Yeung to the police head. Yeung work with another inspector who is a good friend of Yeung himself. Lau sneaked into Yeung's office, stealing the cassette, and ask the head to tell him that Yeung is the spy of the triad, Sam's triad. The inspector friend of Yeung, without found by Lau, changed Lau's own... Written by SangWoo_KwoN
If you loved the first two 'Internal Affairs' movie, then you'll probably find it easy to also enjoy this concluding part: if not, you may find it more difficult. Part one was a tense thriller; part two, more epic in tone, a prequel that filled in the back story, concentrating on some of the secondary characters from the first film. But it's not completely clear where there's any plot left to fill a third part. What this film does is overlay the previous stories with an additional layer of romanticism and complexity; but there's a certain lack of focus to the plot, with almost all of our favourite characters already dead by the end of the second film (although, in flashback, there's a rebirth for the great Tony Leung, absent from part two). Indeed, the film works almost entirely by encouraging us to feel differently about scenes we have already witnessed. I still liked this third story about the quiet men of violence, and it did succeed in feeling like something more than just a repeat of the earlier films. But it's not so clear how much it adds to them.