Lorelei scrambles through the streets of Southampton, where the great airships are built. There is treasure in the trash bins of the rich for those clever and brave enough to scavenge it. Guards prowl the streets, though Lorelei is far too fast for them to catch. But the winter winds blow cold, pushing her ward to the brink of starvation, and orphans are always the last to be served. Hope comes in the form of a broadside—the Imperial Navy is looking for young boys and girls. The Navy always has food, and a chance to see the skies of the world as a ship's rat.

The Dauntless, flagship of the fleet, is a wonderland. Her great sails billow high above the lifting balloon, and far below brass engines gobble coal. Lorelei explores the ship, runs messages, and climbs through the massive balloon and up the rigging perilously high in the sky. She and her fellow rat Bobby visit exotic ports and dodge pirate attacks. They are determined to make their new lives last forever by earning entrance to the exclusive Anglish Imperial Naval Academies. For a ship's rat has only a few short years to prove her worth or be unceremoniously dumped back on the ground.

When the Dauntless is recalled to Londinium to escort Crown Prince William to a war ending marriage with a foreign princess, a chance meeting brings new possibilities. Tom, a royal servant on the run from his own duties, is taught to play the part of a ship's rat. Emboldened by their success, they conspire to map the vents of the Dauntless. This opens the forbidden passenger decks for exploration, and gives them the key to the ship's inner workings. It's the chance of a lifetime, but discovery will see them all groundside for life.

Just three weeks from Londinium to Miyako. What could possibly go wrong?