On Thanksgiving Day, Bart gets the entire family mad at him and runs away from home. When he sees what life is like on the seedy side of town (and ends up on the evening news), he realizes how good things are for him and returns home.
It is Thanksgiving, and Lisa is making a centerpiece for Thanksgiving which honors women such as Georgia O'Keeffe, Susan B. Anthony and Marjory Stoneman Douglas (who worked her whole life to preserve the Florida Everglades). Meanwhile, Bart gets in Marge's way in the kitchen as she is trying to cook Thanksgiving dinner, while Homer watches Macy's Thanksgiving Day Parade and football on TV.
When the guests—Grandpa, Patty, Selma, and Mother Bouvier—assemble at the table, Lisa brings in her carefully-crafted centerpiece and proudly shows it off. Bart brings in the turkey, and he complains that the centerpiece is blocking space for the turkey. Bart and Lisa get into a fight, and in the ensuing chaos, the centerpiece lands in the fireplace and quickly burns up. Lisa runs to her room in tears, and Bart's parents send him to his room as punishment.
After Marge consoles Lisa, she tells Bart he can come downstairs to dinner on the condition he apologize. Bart scoffs at the directive and is told to stay in his room. Bart decides he doesn't have to take his mother's punishment and decides to run away. Homer throws out Santa's Little Helper when he tries to eat some of Bart's turkey, and Bart takes him with him.
First, Bart sneaks into Burns' mansion, where he attempts to grab a freshly baked pie. However, Bart is caught. Bart and Santa's Little Helper then wander to the seedy part of town, and Bart donates his blood plasma at a blood bank for $12.
Bart then goes to a soup kitchen, which is serving Thanksgiving dinner to homeless people. There, Kent Brockman is doing a report on the dinner, where he delivers a self-serving commentary on how the patrons—vagrants, the homeless and alcoholics—are forgotten on Thanksgiving. Later, Brockman interviews Bart, where—on live TV—he mocks his family and refuses to apologize. The family sees the report on TV, and Homer immediately calls the police (well, after he calls the operator saying, "Get me the number for 9-1-1!").
As Bart walks out of the shelter, one of the bums asks Bart if he's got a home. Bart reveals that he stays with "this family" (referring to his own home), and seeing how the bums need the money more than he does, offers the money he got from his blood donation to the bums. A remorseful Bart, realizing how he has more than the bums with whom he shared Thanksgiving, decides to return home.
However, once he arrives home, Bart considers what his folks might say to him. He imagines himself being greeted warmly and offering an apology, but then they scornfully mock him and laugh in his face as he grovels an apology, then begin to blame him for everything (Grandpa being old, Homer being bald, Maggie not talking, America for losing its spirit). Bart decides to wait outside a little bit longer to sort out his feelings.
Meanwhile, as Homer and Marge are interviewed by the police, Lisa is upstairs, writing in her diary and conceding defeat. She begins to cry, after which Bart—who is on the roof—calls her outside. There, the two discuss what happened, and Bart still refuses to apologize at the belief that he has done nothing wrong. Lisa tells him to look deeper. Bart comes to realize that he hurt her feelings by destroying something that she considered dear. Bart apologizes and Lisa happily accepts and kisses him.
Finally, Homer leads the family in prayer, as they thank God for "one more crack at togetherness," as they enjoy an 11 p.m. Thanksgiving of leftovers and displaying the thankful spirit that was absent from the earlier debacle.