Gripping story and a great twist in the end, The only reason I gave 4 stars instead of 5 is for the stupid thing the hero does at the end. When people are dying in the streets due to the gas he can climb the source chimney with cloth tied around his nose without any effect on him and deactivate the chimney. Logic is lost after such a great buildup to the end. I would say the director just shot his own leg by bringing some ridiculous nonsense at the end which was not needed. But still worth a watch go for it.