Lisa's school project leads to the discovery of a new drug that makes the elderly less cranky and more tolerable.

When Flanders' parents prove to prefer Homer's company to his, he jealously responds by giving Homer a shiner, and then tries desperately to reconcile with him. Meanwhile, Lisa is at a loss to understand why a new substitute teacher is bullying her for no obvious reason.

During a research trip, Lisa learns that Sideshow Bob is the chief scientist at a big chemical engineering company; Marge tries to teach a teen church group about healthy sexual practices.