When an emergency keeps Marge from taking Lisa to an about-to-close museum exhibit, Lisa tries to take the bus instead and ends up in an unfamiliar part of town.

!! Tropes:

* AnAesop: Never be afraid to live life on the edge.
* AdultFear: Lisa being missing.
* {{Area 51}}: Or rather, Area 51-''a''.
--> [[NoSuchAgency "You are here. We are not."]]
* BaitAndSwitch
* {{Balloonacy}}: Subverted when Homer needs to get up high to spot Lisa. "Oh, I hope this works...these are for you if you let me use your cherry-picker."
--> "Well, I've already got some balloons - but they're not this nice. Deal!"
* BilingualBonus: The signs in the Russian district of Springfield are actual Cyrillic words and the Russian the chess players speak is real.
* ChewToy: Homer. His quest starts with him trying to save Lisa, and it ends with his head caught between two halves of a drawbridge.
* EarWorm: In-universe. [[spoiler: The music from the Orb of Isis for Homer, even if he gets the tune wrong]].
* IfIHadANickel: Dr. Hibbert subverted the trope. He replaced "a dime" with the amount of money he usually charges for the kind of medical procedure performed on Bart.
* {{Jerkass}}: All Larry the Bus Driver did to help Lisa out is tap the sign that says "Do not talk to driver", even after she truly becomes lost and frightened, before abandoning her in the desert.
* NiceJobBreakingItHero: [[spoiler: Homer accidentally damages the Orb of Isis: subverted when dropping it revealed a music box with a pretty tune]].
* MoodWhiplash: [[spoiler: The nice moment when Homer and Lisa discover the secret of the Orb of Isis is quickly ended when they trigger the alarms and have to escape, right at the end of the episode]].