While attending church Marge notices Maggie scratching herself. Fearing something is wrong, Marge and the family seek out Dr. Hibbert, who’s attending the First A.M.E. Church of Springfield, an African-American congregation. When Dr. Hibbert examines Maggie, he diagnoses her with chicken pox. He tells Marge to coat the baby with Calamine lotion. Later, at home, Homer tries to pick up Maggie, but Marge warns him to stay away from her, as Homer has never had chicken pox. The disease can be dangerous to adults. A sulking Homer makes his way to the backyard. Flanders notices Homer and asks why he seems so glum. Homer tells him that Maggie has chicken pox. Flanders asks Homer if it would be okay for him to bring Rod and Todd over to the house. Neither has been exposed to the disease. Homer realizes that Maggie is a potential goldmine, as parents from all over town will want their kids to catch chicken pox. He throws a “pox party,” and charges $15 for admission. Kirk Van Houten shows up with Milhouse in tow. He explains that Luann will pick the boy up when the party’s over. Marge invites Kirk to join the other parents in the kitchen for drinks. Luann appears at the door to pick up Milhouse. Kirk tries to excuse himself, but Marge talks him into staying. After Luann has a few drinks, she flirts with Kirk, and tells him that she’s not dating anyone. As the party wraps up, Milhouse makes his way to Homer and Marge’s bedroom to retrieve his jacket. When he opens the door, he sees his parents kissing. Milhouse is stunned.

The next morning, during breakfast, Bart tells Marge and Lisa about Milhouse’s “traumatic” experience. When Homer enters the kitchen, he’s covered with red spots. Marge realizes he’s contracted chicken pox. She has him climb into a bathtub filled with oatmeal to help relieve the itching. Unfortunately Homer begins devouring the oatmeal. He phones work to tell them about his ailment, but ends up getting fired. Kirk and Luann tell Milhouse they’re going through what’s called a “trial un-separation.” Milhouse is overjoyed that his family might be reuniting. His happiness is short-lived: he soon realizes that his parents are more interested in each other than they are in him. Milhouse explains his dilemma to Bart. Bart thinks the best solution is to make Luann and Kirk break up again. Milhouse’s first feeble attempts at tricking his parents into separating go nowhere. Later, at home, Lisa watches a Fox television show about teenagers in Orange County. The plotline involves a character planting a bra in order to break up a relationship. Inspired, Bart and Milhouse put one of Marge’s bras in Kirk and Luann’s room. Luann discovers the bra, and finds a small nametag that reads, “property of Marge Simpson.” Furious, Luann tells Homer that Marge has been sleeping with Kirk. When Marge returns home from the grocery store, Homer confronts her. Marge insists she’s not having an affair. When Homer doesn’t believe her, Marge kicks him out of the house. Bart realizes his plan to break up Milhouse’s parents has backfired.

Homer returns to the house to pick up his mail. Lisa tells Homer he can patch things up, and wants to know what led to the breakup. Bart interjects, claiming that sometimes things just happen. This raises Lisa’s suspicions. She accuses Bart of being responsible for the separation of their parents. Bart approaches Marge and admits that he planted the bra. Marge isn’t willing to forgive Homer for not believing her. Desperate, Bart and Milhouse concoct a new scheme. They trick Homer and Marge into meeting at a park. The pair plot to throw a dummy that resembles Bart into a nearby river. Bart thinks it will make his parents realize what really matters: each other. The scheme goes awry when Milhouse accidentally shoves the real Bart off a cliff. Bart plummets down the cliff and lands in a raging river. Homer dives in to rescue him, and Bart ends up riding Homer like an inflatable raft. As they approach a waterfall, Bart admits that he planted Marge’s bra in Milhouse’s parents’ bed. Homer strangles Bart, but moments later Marge stages a rescue mission. She tells Homer he’ll just have to trust her. Marge saves Homer and Bart before they plummet over the falls. Marge realizes that Homer does trust her after all. They hug and kiss.