Homer, envious of Ned Flanders's new motor home, goes to Bob's RV Round-up to buy one of his own, but because of his poor credit rating, he only qualifies for a dilapidated one much to his family's disgust. Thrilled with the new RV, Homer takes his family on an excursion. Driving on remote back roads and ignoring Marge's suggestion to turn back on the main road, the Simpsons find themselves teetering over a precipice. The family escapes the RV before it plummets over the cliff, leaving themselves stranded in the wilderness.
Homer and Bart set out for help, unaware that Maggie is tagging along, while Marge and Lisa stay behind. Separated from Homer and Bart, Maggie is soon adopted by a family of bears. Meanwhile, Homer and Bart plummet into a raging river where they lose their clothes, but hide their nakedness with leaves and mud. Marge and Lisa make themselves comfortable by a campfire, while the boys freeze in the wilderness. The next day, Homer tries to steal honey from a beehive, only to be attacked by the bees, but evades them by jumping into a mud pit. A nature photographer takes a picture of Homer covered in mud, mistaking him for Bigfoot, and soon the forest is inundated with Bigfoot enthusiasts and reward seekers.
Marge, having been rescued along with Lisa by park rangers, identifies the monster in question as her husband and causing quite a controversy. Cold, hungry, and exhausted, Homer and Bart stumble upon the cave housing Maggie and the bears. Homer is soon captured and taken to a lab for testing. The authorities allow Homer to return home after scientists agree that he is "either a below-average human being or a brilliant beast." While watching the news coverage of the whole debacle, Homer worries about the insults he'll receive from his co-workers, until Marge consoles him, calling him "my brilliant beast."