While running away from home, for reasons that are eminently defensible, Emilie's plans to stow away on the steamship Merry Bell and reach her cousin in the big city go awry. Suddenly she's on the wrong ship and at the beginning of a fantastic adveture.

Taken under the protection of Lady Marlende, Emilie learns that the crew hopes to use the aether currents and an experimental engine to journey to the dark interior of the planet in search of her new guardian's missing father. Along the way, Emilie has to make some challenging decisions and take daring action if they are ever to return to the surface world alive.