Tyrone, Uniqua and Tasha live in Filthingham, the filthiest village in the world. Ewww! They all want to take a bath and be clean, but Mayor Stinkypants has banned cleanliness from the village and locked all the cleaning supplies in the dungeon. To make matters worse, today is the Festival of Dirt. More filth! Frustrated, Tyrone sneaks away to the forest to find Robin Hood the Clean. He comes and cleans the village and Mayor Stinkypants learns that it's more fun to be clean. Everyone gets their cleaning supplies back, Mayor Stinkypants lifts the ban on clean and changes the Festival of Dirt to the Festival of Soap!
Uniqua, Tyrone, and Tasha are first seen in the backyard's mud puddle. They are all covered with dirt and grime. Each of the three explain to the viewer how they are the villagers of Filthingham, the dirtiest and stinkiest village in the world. Austin, Mayor Stinkypants, walks up to them and tells the trio that being dirty is good. All four sing Everything is Filthy in Filthingham. After the song is over, the backyard transforms into the village of Filthingham, where everyone is getting ready for "the Festival of Dirt".
The three villagers peek into the dungeon. All of their soap and cleaning items are locked away in it. Tyrone tells Tasha and Uniqua that he has the last bar of soap in Filthingham right in his hands. The girls are glad. Stinkypants suddenly walks up to the villagers for inspection. He checks Uniqua, then Tasha, but smells something funny on Tyrone. He sniffs out his soap and goes to lock it in the dungeon with all the others.
Tyrone can't take anymore of this. He sings, along with Uniqua and Tasha, We Wish We Could Wash. After the song is over, Tyrone heads out to Purewood Forest to find Robin Hood the Clean, the only one who can make everything clean again. Robin Hood was sent to the forest by the mayor of Filthingham because nothing was dirty with him around. Robin Hood spots Tyrone, and thinks that he is trying to stop him. So Pablo (Robin Hood) jumps out to Tyrone to stop him. Tyrone explains to Robin Hood that he has a plan on how he can sneak in and get the town clean again. They sing the song Robin Hood the Clean. Robin Hood refuses. Tyrone tells him that "Mitty", Robin Hood's favorite bath mitt, is locked in there as well. Pablo wants to get started as soon as possible.
Robin Hood disguises as a villager and is not sure if he wants to go along with Tyrone's plan anymore. Tyrone reminds him of Mitty and Pablo dashes into the disgusting village. Robin Hood pretends to be a mud-loving villager in front of the mayor so he is not recognized. After he gets past Austin, he runs into the castle, which the dungeon is located. Robin Hood is shown running into a deep chamber.
Meanwhile, the Festival of Dirt is starting. First, it is time for a game of mud throw. Uniqua throws from a few feet away, and misses. Austin, the mayor, throws from about an inch away and gets the ball into the center of the target. Uniqua is furious and asks Stinkypants why he cheated. Austin answers that he did not cheat, because mayors are allowed to cheat. Uniqua, because of her loss, is thrown into the mud tub, where losers go.
Next, it is time for a game of tin balancing the rules are, whoever can keep their mud pies balancing the longest on their head wins. Tasha loses, and then the mayor reveals that he glued his tins together, because mayors are allowed to.
Finally, it is time for a game of long jump. Austin and Tyrone compete. The rules are, whoever jumps the farthest across the mlong pit wins. Tyrone misses the end, but then the mayor says that he meant short jump, and jumps for a very short distance, and explains that mayors are allowed to change the rules. Inside the castle, Robin Hood has gotten to a dead end. He knows that there might be a hidden door behind all of the mud on the walls. He scrubs away the mud with a toilet cleaner. A door is revealed. He opens it. Robin Hood finds the dungeon. He starts to get everything out of it, including Mitty.
At the festival, Tyrone has lost the game and is about to be thrown into the mud tub where all of the losers will be dunked. He is very nervous. Pablo has gotten out of the castle and has already started to clean the fountain, and fresh water is squirting out of it. He jumps up to the mayor and rips off his villager disguise. He holds Mitty out to him. Pablo creates Mitty's voice as saying "Hello. I'm Mitty. And I love you!". Austin is terrified and tries to walk away backwards from the mitt. He trips over the edging of the fountain and falls into the water, getting clean with all the villagers. Tyrone, now with his Rubber Ducky, tells Austin that baths are fun. Uniqua and Tasha do so, too. Austin realizes it too, and seems to forget about how good being dirty is, renaming the Festival of Dirt to the Festival of Soap. They sing the song The Festival of Soap, while Robin Hood cleans the whole town.
Austin's stomach growls. He proclaims it to be snack time and invites everyone to his house for oatmeal raisin cookies. The village of Filthingham turns into the backyard again as the five friends sing the end song. They all run into Pablo's house. Tyrone, Tasha, and Uniqua open the door after entering and yell, "We're clean!"