The Cyber Ciphers of Eartha Quicksmith: 3

Kip and friends must travel into the molten ocean deep below the earth's crust to defeat the Grittleshanks once and for all. But other challenges lie in wait... final in trilogy. 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.