If you are not someone familiar with the China-Hong Kong relationship, I recommend you skip the film altogether. It will simply not make sense.
The film is basically a metaphor for the relationship between Hong Kong and China, and the exodus of Hong Kong people before the handover. Why they were running away from the "Japanese soldiers", what the red rain means and etc. None of those questions were answered because this is a political film disguised as a thriller mystery. It was never the directors intention to answer those questions.
That makes no sense to me. It's like saying: Skip watching 'Three Days of the Condor' if you're not familiar with American clandestine operations. Well, exactly that's why one would watch a movie like that. It has nothing to do with people being disappointed with this movie. It's not the lack of closure or anything else. It's the movie itself. That being my little, tiny-winy opinion.
On imdb, its about a minibus full of passengers who end up in another dimension where a deadly virus is raging.
That's it. That's all that it is about. The passengers on the minibus are in another dimension in which the nuclear reactor came out. Anyone who was hanging out near the city dies sooner, but it doesn't really explain why some people die and others don't.
Also, it never explicitly tells us they are in another dimension. The phone call from the girlfriend saying he's been gone for 6 years is a hint at this, but there's no pay off or way to confirm everything.
Yeah some kind of Final Destination shyt would have made more sense than the ending given...regardless of it being a metaphor or not, it should have had an ending...the one that was given literally didn't answer ANYTHING. Saying to skip it just because of this supposed allegory that it is doesn't make sense though, because I still found it to be very enjoyable. The humor is interesting and the action was pretty exciting. But when the credits rolled I was genuinely caught off guard because I was waiting for an actual resolution...which never happened.