Dennis hears a pest exterminator is inspecting the school and decides to have a little fun, menacing up a highly convincing Giant Ant costume for Gnasher - so convincing, in fact, that the exterminator shuts down the school for a whole day! Beanotown should be their oyster, as they take full advantage of the Giant Ant's ability to clear the streets - but the exterminator is not so easily deterred, and is quickly on their trail with a secret weapon of his own.