To battle a menacing evil figure, a group of children team up with amazing mechanical machines built by genius clockmaker Karl Indergarten. Karl and Leopold are best friends who fight make-believe battles in the town's beautiful old oak tree. But when Leopold grows up and becomes an evil titan of industry, he loses the most important thing of all--his imagination. Karl, now a genius clockmaker, must use his skills and his own imagination to save not only his friend, but the entire town as well. Karl builds an amazing coterie of mechanical devices--a small but clever mouse, a miniature boat with brave mechanical sailors, a fierce metal flying dragon, and more--to battle the evil Leopold. A handful of children in the village--Toby, Stuart, William, and Agatha--fight alongside these wonderful mechanical "beings" to save the town and the beautiful oak tree where Karl and Leopold once played.