One morning Marge reacts with panic when she realizes Bart and Lisa aren’t ready for the school bus, which is almost on their block. With incredible speed, Marge preps them both, but she’s too late and the children miss the bus. Marge drags Bart and Lisa to the car and speeds off down the road. Unfortunately, Otto misinterprets her intentions, and races the car along a cement channel. Marge cuts him off, only to realize she has stopped in front of the elementary school. Bart and Lisa board the bus nonetheless. Otto suddenly realizes he forgot to pick up a new student, performs a quick U-turn, and peels out. A short time later Otto stops for Francine, a stocky girl with red hair. All the kids aboard the bus agree that Francine will never fit in, but Lisa decides it’s only fair to talk with her. Meanwhile a saleswoman from Springfield Baby-Proofing shows up at the Simpsons’ front door. She shows Homer and Marge items throughout the house that could prove potentially hazardous to baby Maggie. When Homer sees the saleswoman’s cost estimate, he promptly kicks her out of the house. Back at the elementary school, Lisa approaches Francine and politely introduces herself. Francine responds by punching her in the face.

Marge suggests that Lisa reach out to Francine using one of her Malibu Stacey dolls. Later, at school, Lisa notices Francine playing with her own Malibu Stacey… or so it seems. Lisa realizes Francine raided her school locker and stole the doll. Francine then bites the head off the doll, chews it, and spits it out. She then stuffs Lisa into her locker. Meanwhile Homer decides he can baby-proof the house himself. After making his “improvements,” Homer hands Maggie a nail gun… which Maggie then discharges. Homer yells as each projectile narrowly misses him. Marge sees this, and pulls the gun out of Maggie’s hand. Later Homer impresses Marge with his baby-proofing, and determines to share his gift with the world. Back at school, Lisa approaches a group of bullies in hopes of purchasing a bodyguard. When the bullies find out the problem is a girl, they refuse to help. Soon after, Lisa realizes that Francine targets only smart students, and vows to crack the “bully code.” With some help from Groundskeeper Willie and some school surveillance tapes, Lisa studies Francine’s movements, and reaches a hypothesis as to why Francine has been targeting her. Suddenly Francine appears and begins working Lisa over. Meanwhile Homer makes his way through town, selling his baby-proofing skills door-to-door.

Lisa makes some of her nerdier classmates — Milhouse, Martin Prince, and Database — work out so she can collect their sweat. She also swabs some sweat from Drederick Tatum as he addresses Bart’s class. Meanwhile Homer watches a news report, and realizes that his home baby-proofing is so successful it has begun to affect Springfield’s economy, as everyone from baby-crutch merchants to Dr. Hibbert have suffered from the lack of sickly babies. Homer runs out into the street and begs children everywhere to do something stupid so they can injure themselves. Later, at Springfield University, Lisa addresses a group of scientists. She tells them that “the brawny prey on the brainy” because geeks emit chemicals which bring out the worst in bullies. To prove her theory, she releases a caged Francine, who sniffs Lisa’s scent and advances. Lisa sprays ordinary salad dressing into the air, blocking Francine’s smell receptors and rendering her harmless. Later Francine advances on the nerdy scientists.