Satoshi's Electrium Z-crystal goes missing. Rotom (a big fan of an Alolan detective TV show) is prompted to try and find it with Pikachu as his assistant. In the meantime, Satoshi and the other students are all desperate to keep Kaki, the only other Z-ring wearer, from finding out about the missing crystal for fear of his anger. However, the solution to the case may be even more surprising than anyone thinks.