When pop quiz Porter, the meanest substitute teacher in the world, invites Malcolm and Dandy to her house, the boys expect to meet their doom. Instead, she wants them to get rid of a ghost haunting her dolls. Can the boys stop a ghost that refuses to show itself? And can Grandma Eunice help them solve the case?

Cocoa thinks someone is sabotaging her dance rehearsals, she demands that Malcolm and Dandy find out who it is--or else! The boys discover the ghost of an old teacher who hates the new music, the new moves, and especially the noisy boys. Can the Ghost Detectors zap her before the dance recital is canceled?