Joe, a young ticket-collector, is riding the last train out of London on a dark and stormy night along with a meager bunch of passengers. When the train brakes violently and comes to a sudden halt deep in the middle of a forest, it seems they have hit something on the line. But when the driver ventures out to investigate he never returns, leaving the passengers in a state of panic – particularly when Joe sees the driver's mutilated body outside the carriage.

Realising there's something dangerous lurking in the forest, Joe tells the passengers to make barricades to secure themselves in the carriage but soon the deadly creature is stalking the besieged train and smashing through their defences, picking them off one-by-one. Joe rallies his 'pack' of passengers to fight back. During a vicious battle they manage to kill the creature, revealing it to be a hideous mutated fusion of human and wild animal - a werewolf. However, celebrations are cut short when they hear more howls coming from the forest...