When a Monopoly game goes sour, the Simpsons are forced to undergo the supervision of a social services officer to reinforce the ideals of a functional family, but things go horribly wrong when Homer's (and Ned's) Vegas wife returns.
The show begins with a meeting of Springfield Republican Party, chaired by Mr. Burns, plotting what evil to undertake for the week. After a few suggestions, they decide to destroy the environment and scrap all anti-pollution laws.
From the next day onwards, recycling becomes a felony offense. Owl habitats are destroyed. Mayor Quimby pulls the plug, literally, on the Springfield wetlands, sending them swirling down a huge drain. All factories and industries generate vast amounts of pollution, which produces acid rain.
Marge advises the family to stay indoors. Homer's okay with that idea, as long as there is TV to watch. Unfortunately for Homer, the acid rain melts the antenna thereby killing the signal. Homer cannot fix it, due to the acid rain. Marge suggests that they play Monopoly to pass the time. Lisa picks out many different variants of Monopoly, including Star Wars Monopoly, Rasta-Mon-opoly, Gallip-olopoly, and Edna Krabappoly, until Marge decides upon the original version.
The game starts and Bart catches Homer on his lot and Homer, who's pretty much busted, has to pay up. Lisa realizes that Bart is using Lego pieces as hotels. Since Bart bought her a house, Marge takes his side. Bart asks: "Who else is going to take care of her? Dad?" Homer throttles Bart, with Marge and Lisa arguing about and demonstrating how to pull them off. The whole fracas upsets Maggie, who speed-dials the cops. The cops arrive and see the brawl and decide to send in a "Negotia-bot", a policewoman robot, used to break up fights. She tries to break up the fight, but the family keeps fighting. So she envelops them in taffy, to subdue them. They are placed in a jail cell (even Maggie),
Marge sighs that the family has hit rock bottom.
At that moment, a choral note plays and in walks a man named Gabriel, wearing a white suit. Homer, hearing the choral note, assumes Gabriel is an angel, but Gabriel assures him that it is just his pager going off. He introduces himself as a social worker, who is here to bail them out and help them become a family again.
Gabriel soon begins questioning them. He starts off with Lisa, who declares her room is her sanctuary and her family respects this. Just then, Bart, sprayed by a skunk, runs in and uses her sweaters to clean up. Next up is Bart and Bart feels proud that Gabriel is following him around. When it is Marge's turn, she tells him how she loves to cook, although a little creepily. In Moe's Tavern, Homer introduces "Gabriel the angel" to beer and gets drunk and verbally dumps on his family, especially himself. Gabriel has his work cut out for him.
The next day, he takes the Simpsons to a picturesque clearing in the woods (which Homer thinks is Heaven). He then starts to give his appraisals on the family. Marge medicates the family with food. Bart does everything to get attention (at that moment, he has a beard of bees). Homer is, quite simply, a drunken, childish buffoon. Then he tells them that he has hung up their lunch (roast beef sandwiches, a falafel for Lisa, and beer) on top of a tree.
When Homer hears there's beer on top of the tree, instead of climbing it, he gets in the car and rams it into the tree. The tree falls over and slides over a canyon, taking Gabriel along with it. It gets wedged between two canyon walls. Gabriel manages to hold on to a branch. Unfortunately, a pack of wolves and cougars has scented the lunch and they gather under the tree. The Simpsons try to devise a rescue plan, as a family. Homer climbs down; the rest of the family steadies his descent. Giving the wolves and cougars the lunch and beer (not Duff), they manage to climb to safety. They all go home, happily singing We Are Family (with edited lyrics).
As they pull up to the house, they see Amber Simpson and Ginger Flanders, the two ladies whom Homer and Ned married in Las Vegas while drunk in Viva Ned Flanders. Gabriel, in disgust, calls Homer a bad man and leaves. Marge, on being introduced to Amber, gets mad at Homer. After all the excitement, the Vegas wedding had turned out just to be another one of Homer's drunken shenanigans, before Marge had thought she might be getting used to Homer, but not now. Ginger goes to the Flanders' residence and is reluctantly accepted by Ned. Although a widowed Ned is not in Homer's situation, he still has plenty of reservations about this. Homer tries to get an annulment to placate Marge, but Judge Constance Harm denies it and orders him to take care of both wives. Marge throws Homer out, so he moves into the treehouse with Amber, who makes him a sandwich, arousing Marge's jealousy.
Ned is not faring much better than Homer. The next morning, Ned, Rod, and Todd wake up Ginger. His extremely nice, religious and pious outlook almost sickens her, and she responds by snapping at him. At the Simpsons place, "Vegas Mom" tries to warm up to the kids, but they blow her off. That night, a heartbroken Homer can not sleep with Marge and does not want to sleep with his Vegas wife, so he tries to sleep in the doghouse, but he wrecks it. The next morning, just when it looked like Marge was gone forever, she has a word with him and they come up with a plan. They act as if they have fought and Homer goes to Moe's Tavern with Amber and gets her drunk. The next morning, Amber wakes up to find that she has married Abe Simpson (Homer's father), forsaking all others, thanks to a videotape of the marriage. She runs off, along with Ginger (who has had enough of Ned's sugary sweetness), and goes back to Vegas. The Simpsons celebrate their victory as a family.