Stag Night (2008)

After they are kicked out of a strip club, a bachelor party heads to the subway to go to another club. They end up on the same train as two strippers they had seen earlier that night. When one of the guys refuses to stop harassing one of the girls, she maces him. As the train stops to let another train pass, the group pries open the car doors and exits to escape the after effects of the mace.

Before they can reboard, the train drives off leaving them stuck on the subway platform which they soon discover hasn't been used since the 1970s.

Most of the group decides to walk down the tracks to get to the next station. In a case of bad timing, they arrive just in time to see a group of men breaking into the vending machines. When a cop intervenes, he is killed and the murderers spot the kids as they are trying to get back down the tunnel without being seen.

The kids head into the tunnels while the murderes, who resemble Klingons and only talk in grunting sounds, chase them around and kill whoever they can catch. The band of lunatics lives in the tunnels and it is apparent that this is not a new activity for them. As our intrepid band of partiers tries to survive the night, they must work together and face their own inner demons. Will they survive?

The movie sort of exists in it's own sphere as there is no explanation for anything that happens. Who are these people? Where do they come from? Why can't they speak? Why are other subway dwellers subservient to them and how do they stay safe? Why do they keep credit cards and cell phones since they don't appear to know what they are? Why are they breaking into the vending machines when they have no use for cash and appear to be cannibals?