Best friends Kip, Albert, Leela, and Timmi uncover a new series of ingeniously hidden riddles, propelling them on a perilous quest. Aided by big-hearted android Incognita and other unexpected AI allies, they set sail in an extraordinary vessel, The Salamander, on a journey beneath the Earth's crust. As the Grittleshank Cooperative's subterranean smoulderstone mine threatens global catastrophe, Kip faces an impossible choice: stop them or save his captive mother.

With more adventure, more inventions, and a large helping of sideways thinking, this is an action-packed close to the trilogy, following The Ten Riddles of Eartha Quicksmith and The Myriad Mysteries of Eartha Quicksmith.