Piston is a steam train decommissioned from heavier mining work in 1882 and now lives in a small isolated western town. He is the only local train to transport people and mail between towns, and is friends with most everyone who knows him. He is content with living right where he is, but sometimes daydreams about travelling cross country to meet other trains like him. 

The story follows Piston as his quiet lifestyle is upended when a circus caravan, lead by Ringmaster, comes to town. His first reaction is awe, he is as excited as anyone to get to meet the new trains and see the show, and Ringmaster seems to take a liking to him as well. But before long, Piston begins to discover the true horror of the circus caravan's inner workings, why Ringmaster has grown so attached to him since they arrived, and eventually, how he can save them.