While going out for a breakfast to cover some water damage in the bathroom the Simpsons see Apu and his kids in line for the best Pre-Nursery school in Springfield. The admittance counselor (voiced by Simon Cowell), first rejects Maggie for not being able to speak but Lisa is convinced that Maggie can make it after a quick test at home. Simon gives her a second chance with an IQ test and finds out that Maggie is truly very smart...even smarter than Lisa!
Lisa get so jealous of Maggie's intelligence level that she feels lost toward her identity. She tried different new lifestyles such as Goth, Cheerleader, Soccergirl, Cowgirl and a few others. She decides to run off since she feels as if she doesn't belong but she realizes that she doesn't have any money and nowhere to stay. She finds refuge in where else but the Springfield Natural History Museum where she finds a good place to sleep, extra food and the natural geyser as a good shower.
Marge and Homer on the other hand get very worried about her and contact the police for help. They end up finding her clothes at the museum and while looking around there Homer, Marge and Bart get caught in the jumbo human replica's digestive system. All Maggie has to do to set them free is press the red button but she can't seem to press the right one until Lisa reveals herself and tells her which one to push.
The family can't understand why Maggie was so smart in the interview but couldn't figure out which button was the red one. Simon and the school director explain it to them by showing the interview video in slow motion, revealing that Lisa was actually subconsciencly telling Maggie the answer through hand signals. Maggie is kicked out of the Pre-Nursery but Lisa still believes in her high intelligence.