When Arnold has a daydream while playing baseball, Harold tells him he has 24 hours left to live (this pilot was re-made into the episode called "24 Hours to Live")

Arnold asks Grandpa what really happened with his parents, and he finds out that they disappeared after they left the country on a plane, although they might still be alive.

Arnold is sick and tired of everybody performing their April Fool jokes on him (escpecially Helga), so he tries one of his own, but it backfires when it temporarily blinds Helga.

When corrupt developer Schek threatens to buy the run-down urban neighborhood where a fourth grader Arnold lives, and now Arnold and his cool-as-ice best pal Gerald are on the biggest mission ever to save their neighborhood as they go up against a powerful industrialist who invades the city and buys everything in sight so he can knock it down and erect a huge "mall-plex." It's up to Arnold and Gerald to save their neighborhood before it's too late and they'll have to move somewhere else. But with the help of of a superhero and a mysterious deep-voiced stranger, Arnold and Gerald will need to recover a crucial document in order to save their beloved neighborhood at all costs.

Picking up where Hey Arnold! left off, this tells the story of what happened to Arnold's parents.