Tom chases Jerry through the house. The cat gets stuck underneath a chair and gets whacked in the rear with a plank of wood by Jerry. Next, Tom throws a lit firecracker into Jerry's mousehole, only for the mouse to light an even bigger firecracker behind him. Jerry hands Tom a coal shovel and Tom tries to whack him with it, but misses. Jerry eventually holds down on the coal shovel and lets go, causing it to smack Tom in the face. Tom chases Jerry into a mousehole but gets his head stuck, so Jerry fiddles with his lips. Tom pulls his head out of the mousehole. He picks up a phone book and flips to an exterminator ad: "AJAX Mouse Exterminators...One Call....That's All." He calls the number for the exterminator on the phone and pretends to be a human scared of a mouse. Jerry gulps.
The exterminator, Butch, arrives. He washes his hands in the fishbowl. He paints a bolt like a piece of cheese and sprays it with "Essence of Cheese." He knocks the bolt into the mousehole and Jerry, fooled, swallows it. Butch pulls out a magnet and Jerry is attracted to it. Butch pulls out an ax and is about to chop Jerry up, but the mouse replaces himself with Tom's tail, causing the ax to chop Tom's tail instead. Jerry runs into another mousehole. Butch uses a corkscrew to make a hole in the wall, but Jerry touches it with some stray electrical wires, sending out electricity that makes Butch smack himself in the jaw.
Next, Tom sprays some poison gas into the mousehole, but Jerry simply walks out wearing a gas mask. The two cats salute the mouse, but once they realize what has happened, Butch smacks Tom. The two cats run after the mouse, but Jerry pulls out an iron and the two cats run into it, with Butch consuming Tom by accident. Jerry runs into another mousehole. Tom uses a crowbar to lift up the wall partway, then the two work together to lift the wall enough so that Jerry is visible. The mouse hits Tom's foot with a hammer, causing him to drop the wall on Butch's fingers. He plays "Yankee Doodle" by hitting Butch's fingers with the hammer, then hits them hard enough that the cat pulls his fingers out from underneath the wall. Butch pulls out a sledgehammer, then hands it to Tom. Butch tells Tom "Shh" and opens up the vent. When he sees Jerry, he runs inside and tries to catch the mouse. In the process, he ends up not only breaking pieces of the wall off, but also causing a chandelier to fall off and break. Jerry runs out of the mousehole, but Butch pokes his head out instead, causing Tom to hit him so hard that he falls through the floor and get a large bump on his head.
Butch lights a bomb by Jerry's mousehole. The two cats hide by a chair. Jerry picks up the bomb and throws it to Butch, who hands it to Tom. They exchange the bomb for a few seconds before Tom puts it by Jerry's mousehole. Jerry tosses the bomb back to Butch. Butch hands it back to Tom, and Tom hands it back to Butch, but Butch's hat falls off. Jerry hands Tom Butch's hat. Butch takes the hat and gives Tom the bomb. Tom takes the hat and gives Butch the bomb. Butch gives Tom the bomb, who keeps the hat and gives Jerry the bomb. Jerry gives the bomb back to Tom, who gives both the hat and the bomb to Butch. Butch gives both the hat and the bomb to Tom, who gives the hat to Jerry and puts the bomb on Butch's head, then they crouch and wait for the bomb to explode. They realize too late that Butch is wearing the bomb on his head as it explodes.
The two cats go after Jerry as he dives into another mousehole. Butch appears by one mousehole, so Jerry dives back in and runs out only to find Tom at the other end. Jerry dives back in and notices that the cats are both feeling around for him. When they both feel Jerry at the same time, they grab each other's hands. Butch tugs at Tom's hand, hitting him against the wall. Tom tugs at the wall, hitting Butch against it. Butch grabs a broom and begins poking Tom with it. Tom yanks at Butch, dragging him through the wall. Tom hits at the debris but all he finds is a hat--and an angry Butch, who crosses out "Mouse" on his "Mouse exterminator" bag and writes "Cat" instead. Tom spells out "C-a-t. Cat." Once Tom realizes the truth, Butch pulls out a gun and chases Tom out of the house and into the sunset.