The debate is intense: Should Walkerville get rid of the swamp by the river and replace it with a fantastic new shopping mall or build the mall somewhere else? Carlos, representing his class, is given the thankless task of persuading the town council... (more) to keep the smelly old swamp. If he loses the debate, he'll lose to Arnold's pesky cousin Janet! The kids learn that the swamp is an important habitat and natural water filter, but the council's not convinced until... FLOOD!!