In an imaginary past world where the air is populated by transcontinental voyagers, pirates, and beings never before dreamed of by the humans who sail the skies, fifteen-year-old Matt Cruse, a cabin boy on a huge airship that ferries wealthy passengers, meets a dying balloonist who speaks of beautiful creatures drifting through the skies. After Matt meets the balloonist's granddaughter and learns that the man's ravings may have been true, the two embark on an adventure to find the creatures.