When Marge is cleaning out the attic and looking for old things to send away to charity, Homer refuses to let her, prompting Marge to look at all the junk she is trying to get rid of. She shows Homer several skis he never used since buying them after the Nagano Olympics. To spite Marge, he decides to use them, so the family go on a skiing trip. When they are there, Marge decides that she wants to avoid skiing or snowboarding for fear of injury. Ironically, she winds up breaking her leg at the ski lodge when a loose-hanging clock falls on it. She goes to the hospital, and Dr. Hibbert declares that she must stay there until her cast is removed.
In the meantime, Lisa offers to take her place, making a structured plan for Homer and Bart to do some of the chores, which Lisa chooses through a chore hat. Unfortunately, Homer and Bart refuse to do any chores, and when Lisa finally prods them into doing some work, they do so in an extremely apathetic and ineffective manner. Marge is enjoying her time in the hospital, due to getting a massage, among other things. The lazy lifestyles of Homer and Bart have taken their toll on the house, which is now a disorganized, filthy hovel with trash everywhere, and with Lisa struggling to make ends meet. She even calls Marge and asks if she can return, but Marge, who enjoys the lifestyle of lying all day in bed not working, lies to Lisa saying she is still too injured to come back. Lisa, angered and desperate for answers, sees the ghost of Lucille Ball, who has an idea to get revenge. She suggests that she pull a clever trick on Homer and Bart while they are asleep. She does just that, and using green poster paint and oatmeal on the men, she tricks them into thinking that they have leprosy.
The next morning, Homer and Bart are told by Lisa they have leprosy from living in dirty conditions. Lisa hopes this will make them clean up the house, but they do not. After the Virtual Doctor computer program confirms that Homer and Bart indeed have "Leprosy", Homer and Bart panic and decide to visit Ned Flanders. Ned is scared to see that Homer and Bart have leprosy, and so he sends Homer and Bart to a leper colony in Hawaii, where they will be needled and sanded. Once Marge's cast has finally come off (and her excess leg hair has been waxed), she comes home to see Lisa finally finished cleaning the entire house. They decide to seek out Homer and Bart in Hawaii. When they arrive, Lisa admits that she only played a trick on Homer and Bart (though they already know the leprosy is fake because Homer ate one of the sores and found it tasty); however, they want to stay there on account of it being a "free vacation", despite the painful electric needle treatments.