In the cold darkness of a winter's night a Sleeper Train winds its way from Cornwall to London. It's Christmas 1954. A group of Soldiers are returning from a training exercise when the train suddenly stops in the middle of nowhere - a mutilated Bull carcass blocking the line. With their assistance the Bull has been moved out of the way and the train allowed to continue . . . but it continues without its guard - the first victim of something lurking in the shadows . . . and he wont be the last.