Simon Barsinister has developed the Big Dipper, designed to suck up all the water in the world. The first few experiments don't work: it freezes the water, steams the water which brings the fire department around as well as Sweet Polly who hears about his scheme to dry up the world. While she goes to the police, Simon tries again only to see it work in reverse and produce more water, thereby flooding the house. When Sweet Polly comes back with a police officer telling him about the plan to dry up the water, they get to the front door only to have it burst open with water. Polly wishes Underdog were there but he is off getting rid of some killer whales.
Meanwhile Simon makes another adjustment to his machine and it works. He plans to steal all the water in the world and force people to come to him for water. He says he will be the master of the world.