In Mario Bros. Plumbing, Mario is eating a slice of pizza. Luigi tells him to stop eating and that they must clean up or they lose the building to Inspector Klean from the Board of Sanitation. Mario tosses out what is left of his pizza and moves the dumpster aside to pick up a newspaper to toss that out as well. He leaves to clean the rest of the basement and more trash falls out of the chute onto the floor.
Luigi then puts a tub over Clog, who was eating a slice of pizza left on the floor. After a short struggle, Luigi successfully does so and explains to Clog that it's only temporary and that he doesn't have to worry. The CooKoo Bird then announces an incoming train, which rumbles the basement as it passes over.
Just then, the doorbell rings. Luigi must answer it. He opens the door to find Inspector Klean. When Mario asks him if he's evicted any old ladies recently, to which he responds no and that it is also why he is in such a bad mood. Looking around Mario Bros. Plumbing, though, he feels that it might help put him in a good mood. He accidentally bumps into Luigi. Luigi tries to wipe him, but he shoos him off, revolted.
Noticing an old pizza by the area where the Ratigator lives, the inspector walks over to it. The Ratigator pops out of his home and steals his toupee. Luigi successfully shoos the Ratigator away before the inspector notices. The inspector gets up and subtracts fifty points due to how dirty the basement was. Just then Clog zooms around in the tub Luigi stuck on him earlier. When the inspector asks what is under it, the Mario Bros. try not to answer.
After a brief struggle, Inspector Klean grabs it to find Clog. He then subtracts another hundred points for "keeping slimy pets at a location of business." He tells them they might have to leave Mario Bros. Plumbing for good. Later, while Inspector Klean is doing some calculations, Clog decides to go on top of his head. Inspector Klean feels Clog and asks what it is he feels. Luigi quickly says that it was leaky pipes. Before Mario can deny it, Inspector Klean happily subtracts yet another 50 points.
The Ratigator plays with the inspector's toupee. Luigi goes over and tells the Ratigator to fetch a stick, which he throws into his sewer hole. The Ratigator drops the toupee for the stick. Luigi grabs it himself and tells Mario to grab Clog off the inspector's head. Mario calls for him, and he comes over. Mario grabs him, and he then evicts them for "attacking a city official."
Later still, just when he is about to finalize the eviction, Clog decides to come off his head to reveal the inspector's hair had grown back, much to his surprise. While he thinks it was the water from the leaky pipes, Mario tries to explain that it wasn't, but Luigi elbows him before he does. Inspector Klean goes on to tell them that he hadn't had hair since he was five years old. He changes his mind about evicting them and tells the Mario Bros. that they passed inspection, this time. Right after Inspector Klean leaves, the brick wall behind the Bros. bursts apart. Relieved, they decide that "when things are right, they're right."