Trenton Colman is a creative thirteen-year-old boy with a knack for all things mechanical. But his talents are viewed with suspicion in Cove, a steam-powered city built inside a mountain. In Cove, creativity is a crime and “invention” is a curse word. Kallista Babbage is a repair technician and daughter of the notorious Leo Babbage, whose father died in an explosion—an event the leaders of Cove point to as an example of the danger of creativity. Working together, Trenton and Kallista learn that Leo Babbage was developing a secret project before he perished. Following clues he left behind, they begin to assemble a strange machine that is unlike anything they’ve ever seen before. They soon discover that what they are building may threaten every truth their city is founded on—and quite possibly their very lives.

After finding a compass and clues left by Kallista’s father, Leo Babbage, Trenton and Kallista head west aboard their homemade mechanical dragon to search for the missing inventor. The two teenagers hope to find answers about their mountain city of Cove, but instead, they find only a blackened forest, ruined buildings, and a small underground city. Almost immediately, Trenton and Kallista are caught up in a civil war between a clan of scavengers called Whipjacks and the Order of the Beast, people who believe that dragons are immortal and divine. Stranded in a new city, the two friends meet Plucky, a Whipjack girl with mechanical legs, and Ander, a young member of the Order who claims humans are able to communicate with dragons. Can they trust anyone, or have they unknowingly stepped into a trap? And high above in the sky, the dragons are gathering . . .

It's time to take the battle to the dragons. In the third and final volume of the bestselling Mysteries of Cove series, Trenton and Kallista—along with their friends, Plucky, Simoni, Angus, and Clyde—fly their mechanical dragons south toward San Francisco, looking to rescue any survivors from the battle of Seattle. Arriving in San Francisco and investigating the area in secret, the young riders are reunited with Kallista's father, Leo Babbage, who reveals that the humans in the city are working as slaves to the dragons, but that they don't want to be rescued—himself included. He says they are being protected by their new master: a huge, powerful white dragon who lives in an impenetrable tower fortress overlooking the city. Kallista is stunned by the news. Why would her father ever willingly want to work for dragons? Trenton and his friends are confronted by the guards and their mechanical dragons are seized. Evading capture, the young riders escape and begin looking for a way to break the white dragon's hold over the city—and over Leo. Working with the kids from the city, the young riders track down the source of the dragon's power to an underground chamber that is accessible only through an underwater passageway below the tower fortress. With the white dragon watching their every move, Trenton and Kallista will need every bit of creativity and ingenuity they can manage to find a way to retrieve their stolen dragons, enter the tower fortress, and take down the dragons once and for all.