Hoping to turn her friendship with Kyle into something more, Grace Holliday jumps at the chance to accompany him on a pre-New Year's Eve romantic train ride high in the mountains. But a frightening message scrawled on the bathroom mirror turns their romantic getaway into a nightmare. Soon, she discovers that all of the passengers have been lured to the train under false pretenses and that a sinister presence lurks among the luxurious accommodations. When one of the passengers is murdered, and the train becomes stranded in the middle of nowhere, Grace and Kyle find themselves in a race against time to trap a killer before the clock strikes twelve.