This short begins with King-Size in conference with his financial minister when a coded message arrives warning of an planned invasion by cats from the Planet Feline (pronounced Fa Lean). A call for Space Mouse is dispatched, He appears in the conference room instantly. The king orders him to go to Feline, disguised as a cat, and destroy their rocket ship. Space Mouse chooses a Siamese cat disguise.. Before he leaves, though, King-Size hands him a pill telling him to swallow it if he gets into inescapable trouble. When Space Mouse wants to know what the pill will do, King Size claims all he knows is that all secret agents take along some kind of pill for emergencies. Arriving on Feline the disguised Space Mouse goes to the headquarters of the dreaded Meow-Meow to investigate. There he spots their leader Big Tom and his girlfriend Persian Pearl. Thinking quickly Space Mouse impersonates an oriental waiter and brings them drinks. When they order a mouse burger to go with the drinks Space Mouse apologizes saying there is a shortage of mice. Big Tom brags he will be bringing plenty of mice after the invasion of Rodentia. With this space Mouse pumps him for more information but Big Tom gets suspicious. When Space Mouse bows to Big Tom, Space Mouse’s suit rips exposing his mouse’s tail. Big Tom pounces but to Space Mouse’s surprise Persian Pearl conks Big Tom and shows Space Mouse a secret passage. The unconvinced Space Mouse won’t use a route provided by a cat but Persian Pearl pulls off her disguise to reveal she, too, is a mouse – Secret Agent X. Using the secret passage gets Space Mouse outside but since he is now in his standard space suit all the cats recognize him and and prepare to pounce. Space Mouse knows it is time to swallow that pill. He does and become invisible allowing him to get to his spaceship and escape, He sends an emergency message to his King to be ready for the invasion then thinks of a plan that should save the day. Meanwhile on Rodentia hundreds of cats have landed and are running everywhere. In the castle King-Size is still in conference with the Financial Advisor who advises “all is lost” Just then Space Mouse radios in he is landing with a secret weapon – thousands of bull dogs. They route the cats and the King is most pleased.