Matt, a young cabin boy aboard an airship, and Kate, a wealthy young girl traveling with her chaperone, team up to search for the existence of mysterious winged creatures reportedly living hundreds of feet above the Earth's surface.

Aboard "The Boundless," the greatest train ever built, on its maiden voyage across Canada, teenaged Will enlists the aid of a traveling circus to save the train from villains.

When a newborn bat named Shade but sometimes called "Runt" becomes separated from his colony during migration, he grows in ways that prepare him for even greater journeys.