The Simpson family is watching Troy McClure's spin on the bible story of Noah. Marge checks the time and sees that it is getting late and the kids must go to sleep. Bart and Lisa want to stay up and finish the movie, and Marge gives approval under the claim that they must all go to bed at 5:00 tomorrow night. The movie itself continues long into the night and doesn't finish until Bart and Lisa have to go to school the next day.
At school, the students are all having a model UN meeting, with the kids all representing a different country. They are all practicing for the statewide model UN meeting. It starts to go haywire when Bart makes a wisecrack towards Lisa and soon the kids are all fighting each other.
The kids all load into the bus to go on their field trip. Back at home, Homer is checking the mail when he accidentally gets some of Flanders' mail. He learns Ned Flanders has a home business to pick up extra money by selling religious book rugs over the Internet. This gives Homer a new idea to make money: he will start his own Internet service.
On the bus, Bart and Nelson have a fruit race to see who's piece of fruit will reach the front of the bus first. Bart chooses an apple and Nelson chooses an orange. Ralph jumps in, choosing a...banana. While the race is almost over, Milhouse joins in using a grapefruit. It ends up bowled under Otto's brake pedal and when Otto presses on it too hard, it splatters acid in his eyes and he gets blinded. It is not long before the bus goes off the bridge and plunges into the ocean. Otto knows he must go to get help, but he is pulled away through the water current. The kids escape from the flooding bus and they swim to shore on a remote desert island. The kids all fight with each other over whose fault caused their predicament, but Bart brings them all to order by saying this island can prove to be a great time. Bart assigns jobs to them in an attempt to turn the island into a paradise.
It doesn't work anywhere near as well as they hoped. The food patrol hasn't found much for food, and their tree house is anything but stable. Soon, Milhouse returns, screaming over a monster that he's seen. When no monster appears, Nelson chastises him over it. Lisa is concerned about making a fire, but Nelson answers her concern using Milhouse's glasses and a rock. The kids are all getting hungry, and with no food, things are looking extremely bleak. But Lisa remembers a cooler full of food on the bus, which sank to the bottom of the ocean. Bart takes it upon himself to swim down there and grab it. He swipes Milhouse's inhaler and uses it like a respirator to swim down into the bus and he grabs it. Once he returns with the food, the kids jump right in to start eating, but Lisa makes them stop, reminding them the rations are limited and they will need to conserve the food.
The next morning, the kids all plan to dig into the food, problem is, they find that the cooler is empty. Who had eaten their food? The answer seems to be Milhouse, who is asleep and surrounded by empty food packages. Nelson wants to get the food back through cannibalistic means, but Lisa puts herself in charge again, saying Milhouse has the right to a fair trial.
In the Android's Dungeon, Comic Book Guy is disgusted with his intolerably slow Internet service. He sees a pop-up window for Compuglobalhypermeganet, Homer's "Internet King" service and is interested in Homer's promise for uploading faster online porn. At home, Comic Book Guy takes his case to Homer, who soon finds the technical Internet terminology to fly completely over his head.
Back on the island, Milhouse's trial begins. Lisa defends Milhouse and Nelson opposes him. In the end, Bart comes to the conclusion that Milhouse might have eaten all the food, but since there is no evidence to prove it beyond reasonable doubt, he must rule Milhouse innocent. Completely outraged over the verdict, Nelson and the other kids wage a civil war and it means Bart, Lisa and Milhouse are forced to run for their lives.
While Homer brushes up on the Internet, Marge tells him Bill Gates has arrived to see him. The Microsoft chairman informs him the he has become aware of his new service, and choses to buy out his company rather than risk a new competitor. Feeling money is in the cards, Homer agrees. Bill Gates is pleased with the agreement to his proposal, and orders his goons to start trashing Homer's office.
Back on the island, Bart, Lisa and Milhouse are still running for their lives from their classmates-turned-savages. They try to hide inside a cave, but Nelson's troop finds them and in the inevitable moment where the two sides must clash, suddenly the very cave turns out to be the home of Milhouse's long-rumored monster. They bolt from the cave and Martin acknowledges the monster is nothing but a wild boar. The two sides' differences are laid to rest once they discover the boar had eaten all their rations, as evidenced by a food package wrapper on its tusk. Upon seeing the boar licking slime off a rock, Lisa tells the kids their food problems are over; all they need to do is eat the slime that grows on the rock...
...but the kids kill the boar and start eating it instead. Everyone is eating the pork meat around a campfire and enjoying themselves. All except Lisa, who is licking slime off the rock, foolishly thinking it's wrong to eat meat in such a desperate time.
Finally, as the narrator recalls, the kids managed to survive on the island as a coherent society, and eventually they were all rescued and able to return to civilization. How? Well, let's say... Moe.