Danny Cohen and his brainiac sidekick Calvin Waffle are back with a brand-new experiment!Something is amiss in Danny and Calvin's fourth-grade class when their loud, rule-enforcing teacher Mrs. Cakel suddenly transforms into a whole new person. Danny and Calvin decide the only way to find out what's really going on is to spy on their personality-switching teacher. But spying soon leads to a greater mystery filled with dog chasing, jelly-injected donuts, peanut-butter-induced experiments, riddle mania, and more!