"A River Runs Through Bob" is the premiere episode in Season 4, being the forty-sixth episode overall.
To make up for Tina missing her Thundergirls troop camping trip due to being sick, Bob takes the reluctant family camping in the woods. Once they get there, they meet a survivalist couple camping next to them who offer them supplies. Bob zealously intends to live off the land and fishes for a trout, while the rest of the family, much less impressed, borrow food supplies from their neighbors for dinner. Late at night, Bob and Linda go skinny dipping in the river, but become swept away by the strong flow. They wash ashore far down the river naked and lost, and Bob becomes violently sick from the trout he caught and ate earlier. Linda takes charge, demonstrating surprising aptitude in the wilderness, but Bob stubbornly ignores her, insisting in his own skill at wilderness survival.
In the morning, the kids wake to find Bob and Linda missing and borrow some inner tubes and a "Survivalist Guide" from their neighbors to go search for their parents. Tina attempts to follow the Thunder Girls guidebook, but Louise and Gene find the Survivalist Guide much more compelling. At nightfall, Bob and Linda continue to follow the river back to the campsite, while Tina, Gene, and Louise come upon a Thunder Girl troupe campfire. However, Tina defiantly renounces her Thunder Girl membership, quoting from the Survivalist Guide about how such organizations are "cookie selling machines." Bob and Linda make it back to the campsite, with Bob finally praising Linda for her excellent wilderness skills and dubbing her the "Nature Master."
The neighbor couple tell them the kids are in the trailer. It turns out to be a trick, and the couple tells them they have been living in the woods for 40 months and want Bob and Linda to join them. They trap them in the trailer, and Linda attempts to escape by asking to use the trailer bathroom. The kids return to camp and see Bob and Linda are being held hostage. Using the Survivalist Guide, they "weaponize" bees by using Tina's Thunder Girl sash to drop a bee hive through the trailer roof vent. In the chaos of the bee attack, Bob and Linda are able to escape the trailer and the Belchers flee in their car back to the city. Tina finds her combination of Survivalist and Thunder Girls skills helped her save her parents, and re-envisions herself as a "Thundervivalist."