This film takes the traditional Hong Kong route to getting round the problem of how to make a sequel, after everyone has been killed: make a prequel instead (see also A Better Tomorrow III). Here, the calendar is cranked back to 1991, when future boss Sam (Tsang) is some way off the top of the pile, but things are in line for a shake-up after the current triad leader is murdered. We see the early days of Yan (Yu), the cops' deep-cover man in the criminal world, whose brother Hau (Ng) becomes the new boss. Meanwhile detective Wong (Wong) adopts a 'by any means necessary' approach to getting Hau, which has the definite potential for blowback.
Taking place over six years, ending with the 1997 Chinese takeover, the obvious touchstone is The Godfather, which had a similar multitude of threads and characters, though Affairs covers both sides of the law. Fortunately, this sequel (much like Godfather II) almost matches the high standards of the original, thanks to uniformly excellent performances, and one of the best soundtracks I've heard in a Hong Kong movie. Of course, the "mole vs. mole" concept is no longer as fresh as it was, and for the first 20 minutes, you probably won't have a clue, particularly if it's been a while since you've seen part one. But it's worth hanging on, since some moments, such as the final face-off between Sam and Hau, will definitely stick in your memory. IA III is also out; interestingly, several reviews suggest it sucks, much like Coppola's third stab, but sure we'll get round to it eventually.