(When we last left our heroes, Jeff and Britta's steamy love session was interrupted by Abed, Annie and Dean Pelton's announcement that they'd discovered a map leading to Greendale's mythical buried treasure - a fortune that could save the school from the grips of Subway's campus buyout.)
The Dean shows the group an old film reel about Russell Borchard, a computer genius who used his vast fortune to open a computer school that would later become Greendale Community College. Borchard was working on an advanced computer (made entirely of gold) that could read human emotions. According to the legend, Borchard had a secret vault in his hidden office that contains enough money to save Greendale. If the gang finds the secret wing of Greendale, they can obtain Borchard's treasure and save the school! A secret vault in a secret office in a secret wing of the school. Got it? Good.
Shirley and Hickey procure blueprints of the campus and quickly discover an unmarked passageway in the teacher's lounge. This could be the hidden wing of Greendale they're seeking! Hickey smashes a hole in the wall, but there's no secret passageway. Jeff chooses this inopportune time to announce that he and Britta are getting married, which infuriates Annie. Before the conversation can escalate into an all-out war of words, Abed discovers a secret trapdoor under the carpet!
The gang has managed to unearth Greendale's lost wing, but they'll still need to track down Borchard's office and find the hidden vault. Annie is still distracted by the news of Jeff and Britta's engagement, and Abed tries to ease her mind by reminding her that if Greendale were a TV show, this would be the characters' natural reaction to what seems like an ending. It's a strange method of comfort, but somehow it makes Annie feel a little better.
Dean Pelton discovers a jukebox, and Abed quickly deciphers the secret code. By hitting track 127, "Open the Door," by The Secret Doors, he activates a secret door that leads to Borchard's old office, which contains Borchard's mythical golden computer. Much to their surprise, they also find Russell Borchard himself! Greendale's first dean has been isolated in the hidden wing of the school for the past 40 years!
Borchard is happy to have some company, but he's reluctant to let the gang take his golden computer as leverage for saving Greendale. Luckily, he has several million dollars in cash that he's perfectly willing to give to the committee. Unfortunately, the school board guys arrive, seize Borchard's money, break his cherished golden computer and trap the gang in Borchard's isolated office.
Just when it seems like all is lost, Jeff discovers a deed that declares Russell Borchard as the rightful owner of Greendale. The gang escapes from Borchard's office and, by presenting the newly discovered deed, they stop the school board guys from signing Greendale over to Subway. Greendale is officially saved!
With the end no longer nigh, Jeff and Britta cancel their marriage plans. Chang gets a job with the school board and immediately steals Borchard's millions while everyone else dances to Dave Matthews, reminding everybody of the most important lesson of all: the Asscrack Bandit is still out there... somewhere... lurking in the shadows... watching... and waiting.
In an epic season finale, the Save Greendale Committee embarks on an epic journey to actually save Greendale.