After the battle of Seattle, Trenton and Kallista- along with their friends Plucky, Simoni, Angus, and Clyde- fly their mechanical dragons south toward San Francisco, looking for any sign of Kallista's father Leo Babbage.

Arriving in a new city, the young riders investigate the area in secret, only to be reunited with Leo Babbage, who reveals that the humans in the city are working as slaves to the dragons. What's more, the humans don't want to be rescued- himself included. He says they are being 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 work for dragons?

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 enter the dragon's tower fortress and break its hold over the city- and the world- once and for all.

Hard cover.