In the loop-line subway of a city, Dao, Gao Fei, Han Xiao and others suffered a bizarre accident, falling deep into the ground and being attacked by huge monsters. Everyone was very confused at first. Till the teammates were killed one by one, they only started to unite as one, fought against the monsters together, and finally managed to escape. Besides tight and tense plot, there are some humorous comedy elements, which makes the whole story better. It mainly shows the different reactions of people of different identities and personalities in the face of sudden disasters, as well as relationships and emotions between people in disasters.