Our protagonist WuShi and his friends are onboard a highspeed rail train, which is a tourist attraction that goes through the belly of the sea. What they do not know is that once upon a time, the train is a vehicle for time travel experience.

Enter a bloody cycle of fate deep under the ocean. Will you become everyone’s salvation? A train shuttling underwater carrying students and teachers on a graduation trip is suddenly trapped in a strange time loop, endlessly experiencing the moment of a derailing accident . . . The joyful journey quickly spirals out of control when the train derails, locking everyone in the moment of the bloody incident that endlessly repeats itself. WuShi happens to be the only person that remembers each and every fateful cycle. But what’s even stranger — with each repeating cycle, one more of his classmates dies before the train’s derailing moment. A mysterious murderer has appeared, and in the name of deliverance hunts down and kills Wushi and his friends . . .