A group of tired commuters have caught the last train home, ready to hop into their beds for the night. However, their train soon veers off-course and crashes into an abandoned tunnel. The three surviving commuters; withdrawn mother Yi Ling, her son Lucas, and student Janice, are forced to band together and survive the night, as well as avoid the mysterious monster hunting them. Yi Ling still suffers from flashbacks to the car accident that killed her husband and nearly took Lucas` life too. When Lucas is snatched away by the monster, her maternal instincts are tested, and Janice`s ideas ...