Bart and Milhouse pay a visit to a joke shop, where Bart purchases several novelty items, including a fake water faucet, a toucan beak and Frankenstein bolts. When the novelties start popping off his face and neck, Bart decides that only a strong adhesive will work. He obtains a tube of industrial strength glue from Homer, and uses it to adhere the props. Meanwhile, Lisa and Marge prepare to spend the day viewing an exhibition of rare Egyptian items at a museum. But their plans come to an abrupt halt when Bart realizes the novelty items won’t come off his face. As Marge leads her son outside to drive him to the hospital, Lisa asks her mother if she can ride the bus to the museum. Marge does not give her consent. Not to be dissuaded, Lisa phones Homer at work and tricks him into granting her permission. Lisa takes the bus to the end of the line—only to realize she boarded the wrong bus.

Though unfamiliar with her surroundings, Lisa sets forth on a quest to find the museum. Her journey takes her through a deserted industrial area, and later, a Russian neighborhood. Meanwhile, Homer realizes he should not have granted Lisa permission to board the bus alone, and sets out in search of his daughter. Unable to locate her in the crowded streets, he accesses a cherry picker and climbs high above the masses. He spots Lisa in the crowd, but inadvertently presses the wrong joystick, sending the vehicle rolling backwards down a steep incline.

Lisa chases after her father after the cherry picker rolls off a pier and floats downstream. She convinces a draw bridge operator to lower the bridge, which catches Homer’s head between its two halves. Lisa apologizes for taking the bus, and promises never again to take risks. But Homer counters that risks are what make life worth living. To prove his point, he breaks into the museum so his daughter will have a chance to view the exhibit. There the pair observe the mysterious Orb of Isis. Archeologists have studied the orb for decades but have been unable to determine its meaning. Homer accidentally bumps into a support pole holding a velvet rope, triggering a domino effect that causes the orb to roll off its pedestal. The orb opens, revealing that it is really a music box. Homer replaces the orb and he and Lisa make their way out of the museum.