T.J. finds a treasure map in an old history book that Miss Grotke gives him; he recruits the rest of the gang to find it. However, this soon leads to having to assemble several different, non-affiliated factions to get to the treasure.
Miss Grotke is distributing history books amongst the class, when she runs out of new ones she's forced to give T.J. an old one, with which he'll have to make do. Opening it, it claims that "man will never walk on the moon." After trying to find the glossary, he discovers a map and a small paragraph explaining the map's purpose at the back of the book. At recess, he shows the treasure map to the gang - telling them not to tell another living soul. It comes with a number of clues that will direct them through the playground and to the treasure.
Gretchen leads them through the clues; however, Miss Finster notices their movements, and reports this to Principal Prickly, who writes them off as childish strangeness. Even so, as Miss Finster leaves, he ponders over their counting of paces. The final clue leads the gang to the fence surrounding the playground. Gretchen reveals that, when the map was created, the playground was much wider than it is now, and so the treasure is buried under the faculty parking lot. T.J. suggests consulting diggers Dave and Sam for help, who suggest digging a tunnel from somewhere else. T.J. suggests the Ashleys' Clubhouse, and the girls agree in return for an equal share of the treasure, and for their possessions not to be covered in dirt. The gang obey by carrying the dirt out in turns and dumping them inconspicuously around the playground. However, Mikey accidentally attracts Randall's attention, and blurts out the situation. Randall agrees to keep quiet, in exchange for an equal share, and becomes a lookout. This makes Finster suspicious again, but once again Prickly sends her away.
Inside, however, Vince excuses himself from class to go to the bathroom, Spinelli becomes suspicious and also excuses herself. After confronting Vince, Spinelli proposes that they team together to dig up the treasure to keep it for just the gang, he accepts. However, the others members of the gang catch them before they can, and they make their way to the clubhouse together. Once there, they find that the Ashleys, Randall and the Diggers are already there, and they fight over the treasure. In the scuffle, the chest is broken open, to reveal a collection of old toys and a letter, which explains that a bunch of kids had put these for which future kids can play. Feeling horrible for the way they acted, they agree to put their own toys in the chest, after playing with the old toys that is.
In his office, Prickly makes a call to an old school friend, to tell him that they found the treasure at last, revealing that it was them who hid the treasure in the first place, 40 years, 6 months, 7 hours, 12 minutes and 26 seconds before.
- Coloring error: When the gang arrives at the facuilty parking lot, Spinelli's hat turns red.
- Coloring error: When the gang finds Randall in the Ashleys' clubhouse, Ashley B.'s skirt is green.
- Coloring error: When the Diggers find the treasure, Ashley T.'s legs are bare, but the top of them is still colored green, making it appear as if she were to wear leggings.
- When the gang finds the letter in the chest, the letter is shown incomplete but Gretchen keeps reading it.
- There are a total of five clues.
- There are several clues to the treasure that take the gang around the playground:
"Climb and conquer the iron beast then turn your attention to the East." - This refers to Old Rusty.
"Look to the backdoor but don't go in; go around the corner to the garden of Quinn." - Mr. Quinn, Third Street School's first Kindergarten teacher, used to keep flowers before he went insane. In the present, a trellis is all that remains of said garden. It's located within the Kindergarten area of the playground.
"The treasure is close so don't think of stopping, go to yon box and beware of cat droppings." This refers to the sandbox.
"A hundred paces across the lawn; but hit the curb too far you've gone. Dig with seal measure for measure because you're on top the Third Street treasure." This refers to the treasure being below the parking lot.
"No grown-ups have ever read these words. Congrats! You found it! Hats off to you. You found the treasure of Third Street School. We, too, were just kids, Third Streeters like you. We found the treasure then buried it anew. But not before we dropped in some toys that brought to us all an assortment of joys. So play with this stuff then dump it back in for future Third Streeters to hunt down again." This is the message that is read by Gretchen; however, it isn't written on the note that's found. This message was imposingly written by Petey P (Prickly.)
- When faced with having to find a way under the parking lot to get the treasure of Third Street, Spinelli reveals that an Uncle of hers is in "the construction business" and can get the gang some dynamite.
- This was the final episode to be written by Peter Gaffney.
- It is stated throughout the clues that each one has been found by a different group of students going down the generations.
Second clue: yonder is a middle-English word that means 'over there.'
Third clue: the clue itself being explicit in this fact: the treasure is buried underneath the concrete. Which would mean a group buried it there another group found it and re-wrote it so others would know.
Fifth (and last) clue: it states that explicitly that other groups found their predecessors and a successor will find this one.
- Ashley T. is the only Ashley (not including Spinelli) to not have a speaking role in this episode.
- If one was to work backwards from this episode's air date, then the treasure was last buried on June 15, 1959. However, since the series takes place in the 1997-98 school year, the treasure was actually buried some time in 1957, which makes better sense since Prickly was born in 1947 (as mentioned in "The Hypnotist") and therefore, he was in fourth grade in the 1956-57 school year.
- T.J. Detweiler - Andrew Lawrence
- Vince LaSalle - Rickey D'Shon Collins
- Ashley Spinelli/Kindergartener - Pamela Segall-Adlon
- Gretchen Grundler - Ashley Johnson
- Mikey Blumberg - Jason Davis
- Gus Griswald - Courtland Mead
- Miss Finster - April Winchell
- Miss Grotke - Allyce Beasley
- Principal Prickly - Dabney Coleman
- Randall Weems/Digger Dave - Ryan O'Donohue
- Digger Sam - Klee Bragger
- Captain Sticky - E.G. Daily
- Ashley Armbruster - Anndi McAfee
- Ashley Boulet - Francesca Smith
- Ashley Quinlan - Rachel Crane