It's been a while since we've seen the girls, but they're back in the museum. They're all freaking out because the lights are out, the mouse is gone, and the dinner plate is missing. Everyone's worried about the missing plate, but the girls don't know what to do. The girls' teacher has been worried about them, and they've been trying to figure out what's wrong with the plate. They can't figure out how to fix the power problem, so they'll have to search the bag for the missing thing. They all agree that it's a crime, and that the thieves must have gotten away with it. They agree that the painting must have been stolen, but then they realize that there's no way to get it out of the museum without the girls' help. They decide that the only way out is to break into the museum and steal the painting.