For monster sleuths Tank and Fizz, proving fourth-grade bully Rizzo Rawlins is planning to cheat in the upcoming Battle Bot Cup should be a piece of cake. But cake crumbles fast, and the case soon leads the detectives to a mysterious hacker known only as the Codex, who threatens all of Rockfall Mountain with a very dark fate. With the help of their wizard-in-training partner, Aleetha, Tank and Fizz leap into action, dodging deadly battle bots and sinister spellbooks in a race to stop the return of a very angry ancient demon. Fans of the first book, Tank & Fizz: The Case of the Slime Stampede, will blow their circuits with this gadget- and magic-filled robot mystery.