Near the top of the mountain, Little Engine is immobilized when her water tank goes empty. A black train appears and offers to take the toys and Richard (the real boy) to the real world, which she accepts. However, once they were in his boxcar, the black locomotive reveals his true form as the Nightmare Train, having tricked Little Engine. She demands him to let them go, only for the Nightmare Train to push Little Engine off the tracks, leaving her derailed. He intends to keep Richard and the toys in Dreamland to keep the tunnel closed and halt the delivery of good dreams, so the only dreams that could be delivered were his nightmares.
Inside of the Nightmare Train, the toys and Richard suffer hallucinations of their worse fears. After standing up to the illusions of his bullies, Richard falls from the Nightmare Train after a failed attempt to uncouple the cars and is found by Little Engine. When the Nightmare Train confronts them, they free the toys with the Nightmare Train in pursuit. The Nightmare Train was eventually defeated when Richard and the toys pull a lever to switch the tracks, sending him barreling down the mountain at high speed.
During the end credits, the Nightmare Train is shown at the bottom of a ravine, probably having jumped the tracks because of Little Engine and her trick. His fate afterwards is unknown.
As his name implies, the Nightmare Train is a very frightening and malevolent engine who has a strong desire to deliver nightmares to anyone. He exhibits an extremely manipulative and deceitful personality, as he deceives Little Engine into giving him the toys and Richard. He is also shown to be outwitted by Little Engine, as he takes a wrong track.
The Nightmare Train is a large black anthropomorphic 0-6-4 tenderless steam locomotive with three smokestacks and yellow creepy eyes with red pupils, pulling a train of three old rickety boxcars and finally one old rickety caboose. As soon as he had the toys and the real boy in his possession, his appearance changes into a more frightening form with his cowcatcher forming his mouth and other bestial features like his whistle and pistons. Even though he has a whistle, he has a diesel horn.
The Nightmare Train's disguise form.
The Nightmare Train's evil grin (Sweet Dreams).
(Little Engine: Let my friends go!") "Not gonna happen!" (shoves Little E off the track)
"You haven't the sense to give up when you should!"
Although the Cave (although not truly evil) is the main antagonist of the 1991 The Little Engine That Could film, the Nightmare Train appeared to be a more evil villain, having bigger plans, had more screen-time, and turned out to be more dangerous than his predecessor. Whereas the Cave was a neutral character since he appeared to be the fear of the mind of the 1991 film's main protagonist Tillie.
Despite having a whistle, the Nightmare Train has a diesel horn, something that isn't common for steam locomotives.
Despite being the main antagonist of the film, the Nightmare Train has a few minutes of screen-time.