'Nightmare' is only the second Korean horror movie I have seen. The first was the overrated 'The Eye', which many people seem to love (I don't). Personally I enjoyed this less known supernatural thriller a lot more. It owes a huge debt to classic American slasher movies of the past, but they themselves were inspired by Italian giallo, so it doesn't really matter who did what first, as long as it entertains. And this very effective thriller does that. I can see certain superficial similarities between 'Nightmare' and the much hyped Japanese horror film 'Ringu', but the approach is quite different, and I think this is the better of the two movies. The story concerns a group of school friends hiding a secret from the past, which comes back to haunt them. Standard horror fare true, but 'Nightmare' makes this familiar material worth watching just the same. And having a few very cute Korean girls among the cast certainly does it no harm! Worth a look, it's better than you'd think.