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 The three surviving commuters; withdrawn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 of family are challenged as she remembers her difficult
relationship with her estranged father. Back at the subway control
headquarters, the engineers do their best to make sense of the situation
and rescue the survivors.