When Marge swears off becoming friends with couples, after Homer insults the new neighbors, Lisa declares she doesn't need friends either, making Marge recant her previous promise.
Marge is making a Red Velvet Cake for a block party, but at the same time, Bart is watching an Itchy and Scratchy cartoon on a portable TV. Bart turns up the volume on his TV to drown out the sound of Marge's mixer, and Marge tries to counter by turning the mixer speed to full, only to end up making a mess and having to go to the store (in disguise) to get a store bought cake.
At the block party, Marge meets Booth Wilkes-John, a British man, who invites Marge over to adult game night with his wife. Even though Marge wants to go, she thinks back to when Homer ruined another adult game night for her. Marge declines, at first, but later talks to Homer in bed about not having any friends, so she wants to go to this game night, yet Lisa chimes in with being okay with not having friends herself. Before game night, Marge reminds Homer of the proper etiquette.
At Booth's home, Marge and Homer mingle with the guests. The game begins with role play, and Homer unknowingly reveals the murderer in the story prompting Booth to kick Homer and Marge out of his house. Marge feels depressed over not having friends, but she is set on not having Lisa go through life without friends. Marge chooses to stage a party for Lisa and invite everyone who is familiar with her. The only problem is that only one boy comes to the Simpsons house. Marge plans to scrap the idea, but the guest won't leave unless he gets a party. Marge and Homer throw the party for the party animal and send him off with party favors just in time as Lisa arrives home. At Springfield Elementary, Marge goes on a mission to figure out why Lisa does not have any friends. Miss Hoover spells it out very clearly to Marge that no one in Lisa's class likes her for being to isolated and insistent in getting everyone to accept her views. Marge refuses to accept that and tries to find someone who does. When the class has to practice square dancing, Lisa is left without a partner until outside student named Tumi steps in.
It is soon discovered that Lisa and Tumi share the same interests. However, Bart quickly becomes suspicious and believes Lisa is being duped. When he follows Tumi to Krusty Burger play area, he learns the truth when he witnesses someone handing over some cash to Tumi and takes photos of the entire exchange. Bart delivers the photographic evidence to Lisa, who finds out that Tumi was being paid by Marge to be Lisa's friend and she confronts Marge for her behavior. Marge tries to express her sorrow, but Lisa refuses to forgive her.
Soon, Abe reveals that he paid Lenny and Carl to befriend Homer in the sandbox and to this day they are still friends, much to Homer's (at first) dismay. Later, Marge has a heart-to-heart conversation with Lisa, but she still refuses to forgive Marge and intends to tell every counselor about her evil deeds. Marge is in tears, which makes Lisa secretly proud and plan to use her newfound tactic to get what she wants in the future. Eventually, the thought of her mother in tears makes Lisa offer a genuine apology and forgives Marge.
The next day, Tumi apologizes to her for her behavior and why she accepted the bribe from Marge for payment on a new belt. She also admits she does like being friends with Lisa. Lisa forgives Tumi, but asks for her to be more honest with her from now on. However, Lisa ditches Tumi after she states of her fond to horse meat.