Lisa tries to befriend a new student, only to become the target of the girl's violent outbursts. When the bully, Francine, beheads Malibu Stacey, Lisa vows to get to the root of the problem. After scientific research on typical bully targets (i.e. nerds), Lisa discovers that it's the nerd scent that sets off Francine and the other school bullies. Lisa invents an antidote and is hailed a heroine by geeks everywhere. Meanwhile, Homer becomes driven to protect the babies of Springfield with his cheap and easy safety devices - which drives the "injured baby" industry out of business.