Milhouse's relationship with a new girl at Springfield Elementary, Samantha Stankey, spend all of their free time together, him without spending time with Bart, much to his friend's irritation and their friendship becomes more distant in the process. Meanwhile, Homer tries to lose weight by listening to a subliminal tape.
After a close encounter (Indiana Jones style), Bart manages to retrieve Homer's jar of change to take to school. Bart makes his way outside the house where Otto was waiting and boards the school bus leaving Homer shouting angrily at Bart as the school bus drives away. His best friend, Milhouse, is holding his Magic eight ball. Bart asks the ball whether he and Milhouse will still be friends by the end of the day, and the ball predicts 'no'. Both are puzzled by how this could happen.
A new girl from Phoenix called Samantha Stankey starts at Springfield Elementary School, and Milhouse falls in love with her. To Bart's dismay and anger, Samantha reciprocates, and the couple spend all of their free time kissing in Bart's treehouse. They ignore Bart, and he takes off.
Meanwhile, Lisa is watching a documentary on the health problems of obesity. She is fearful that Homer's obesity will lead to an early death. On Lisa's suggestion, Marge orders a subliminal weight-loss tape for Homer. Humorously enough, the company is out of the tapes and sends Homer a "Vocabulary Builder" tape instead. Homer ends up eating more than ever, but his vocabulary is through the roof. When he realizes that the tape is hopeless he gets rid of it, and his vocabulary quickly returns to normal.
In order to restore the previous status quo, Bart tells Samantha's father what's happening. Mr. Stankey rushes to Bart's treehouse and takes her away before she can even explain. She is sent to Saint Sebastian's School for Wicked Girls, an all-girls convent school. Milhouse is depressed and Bart feels guilty for his actions. After failing to get help from Homer(frustrated over the vocabulary tape), he turns to Lisa for help who is watching a documentary on a possible five finger evolution. When she learns his actions towards Milhouse and Samantha, Lisa berates Bart for humiliating them with his behavior. She tells him to do the right thing and confess or she will tell on Bart to Marge and let him deal with the consequences. He visits Milhouse and confesses that he snitched on him and Samantha to Mr. Stankey. Humiliated, he and Bart fight over Bart's actions much to the delight of Milhouse's parents. Then Bart ends the fight by hitting Milhouse with the Magic eight ball, destroying it in the process and calming themselves down. Milhouse visits Samantha at the convent school and Bart apologizes to her, but she say it's OK - she loves Saint Sebastian's. However, she still has feelings for Milhouse and gives him a farewell kiss, despite her knowingly violating school rules.