After learning that their father really died of lung cancer, Selma and Patty agree to quit smoking. When Selma relapses, an angry Patty moves in with Marge and Homer. 
Homer, Bart, Lisa, Maggie and Grampa are watching television when Marge turns off the TV and tells them that it's her mother's 80th birthday and the family should visit her, but Homer doesn't want to go, claiming that the Bouviers hate him, but he ends up going anyway. At Jacqueline's house, she reveals that her husband, Clancy, died because of lung cancer. This information shocks Patty and Selma, who plan to quit smoking for good.
At the DMV, Patty realizes how hard it is to quit smoking after years of addiction and having a stroke. She also realizes that Selma is not affected by the sudden change of habits and plans to consult Dr. Hibbert. At the hospital, Patty discovers that Selma relapsed ten minutes after quitting smoking.They fight and Patty moves to the Simpsons' house for a while.
Homer gets annoyed by Patty's snoring and walks into the bathroom while she's taking a bath (which makes him spill bleach on his and Bart's eyes). At the apartment, Selma had to make a hard choice: Quit smoking and reconcile with Patty or carry on smoking and lose her sister's respect. She chooses to quit smoking and they both reconcile.
At the end of the episode, it is shown that Patty and Selma started smoking again, as it's easier to cover the bad smell coming from the apartment than to clean it up.
On a subplot, Maggie befriends a squirrel, who introduces her to other animals, such as an owl, a possum and a parrot (which is revealed to be Duffman's parrot). Cletus captures the possum for dinner and puts the captive animal under a dog's surveillance. Maggie makes a plan (with a little help from Plopper, the Spider-Pig) to fight against the Spucklers and free the possum.