Class 3 are sure that something is very wrong when Mr Majeika leaves school without saying goodbye. When they find a message from him saying he's been arrested by the Silly Crime Squad, they are determined to rescue him. To do this they must outwit Hamish Bigmore and Mr Majeika's old enemy, Wilhelmina Worlock. They succeed and Wilhelmina is punished with a 'spell' on earth as a Supply Teacher!