Bart uses an experimental device to make Marge stop her nagging forever, but the entire town of Springfield starts nagging him instead.
Bart wakes up to find Marge on another nagging rampage, leaving him miserable as he heads to school for their field trip to Frink Labs. Prof. Frink demonstrates his new behavorial modification ray, which can alter the behavior of anybody it hits. When Bart demands that he be allowed to try it, Frink tells him that letting him would be irresponsible, then leaves him behind as the tour continues.
Bart uses the ray and comes home to find a happy Marge giving him money for ice cream. As he heads out, Ned Flanders tells him that the lawn is due for a mowing. Nelson and Milhouse also nag Bart about his messy room and refusal to do homework, while Mr. Burns demands that he deleaf his gutter fixings. Bart realizes that the ray has now made everybody in Springfield as naggy as Marge was and runs to the one place where no one will find him.
At the library, Bart runs into Lisa, who wasn't affected due to her overachieving and tells Bart that the only way to break the nagging cycle is to give them nothing to nag about. With no other choice, Bart runs home and begins cleaning, wiping, and waxing his entire room as he moans about feeling like he's trapped in a nightmare...
... and he is. The whole story was dreamt up by Principal Skinner, until is rudely waken up by his mother and told to clean his room before getting to school.