"Circle" opens with 50 strangers waking up while standing in front of an alien-like contraption.
The machine doesn't allow any of the strangers to move beyond the circle they're standing on, and they weren't allowed to touch the person next to them either. It will kill someone every two minutes, randomly, unless at least one of the 50 strangers votes for someone to die using their hand.
As the movie progresses, revelations come out and pacts are made as all of the participants fight for their survival.