Will Everett has dreamed of adventure all his life. Finally, he prepares to take his first journey: to cross the country on the Endless locomotive, the most magnificent train ever built by man. On the way, William accidentally witnesses a murder and becomes the owner of the key to a carriage with priceless treasures, and thus finds himself in mortal danger. Circus performers who are also traveling on the train come to Will’s aid. Now together they need to get through the entire locomotive without getting caught by the villains in order to find William's father in the first class carriage and save the "Endless" from robbery.