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.

As members of the first crew of astralnauts, Matt Cruse and Kate De Vries journey into outer space on the Starclimber and face a series of catastrophes that threaten the survival of all on board.