After finally striking a deal with NBC over their sitcom pilot, Jerry, Jerry and George are faced with having to leave New York City for California. Before doing so, they decide to take NBC's private jet to Paris with Elaine and Kramer, for one "last hurrah". Unfortunately, Kramer causes engine troubles by hopping up and down on the plane while trying to get water out of his ears, nearly killing the four friends in a crash. Upon what looks to be their final moments of life, George reveals he cheated in "The Contest", and Elaine tells Jerry "I've always loved you" but realises the pilot regains control at the last second in mid-sentence, and adds, "-nited Airlines. They make an emergency landing in the small, fictional town of Latham, Massachusetts.
While killing time in Latham, waiting for the plane to be repaired, they witness an overweight man getting carjacked at gunpoint. Instead of helping him, they crack jokes about his size while Kramer films it all on his camcorder, then they proceed to walk away. The victim notices this, and tells the reporting officer. The four main characters are then arrested for violating a fictional Good Samaritan law that requires bystanders to help out in such a situation.
A lengthy trial ensues, bringing back many characters from past shows as character witnesses testifying against the group for their "selfish" acts from throughout the series. The Virgin, the low-talker, the Bubble Boy, Babu Bhatt, the Soup Nazi, Susan Ross' doctor from the night she died, and several others are called to the witness stand, among many more enemies and acquaintances. The four are found guilty, and sentenced to a year in prison, with Judge Arthur Vandelay (Art Vandelay is George's fictitious alter ego) proclaiming: "I can think of nothing more fitting than for the four of you to spend a year removed from society so that you can contemplate the manner in which you have conducted yourselves."
In the final scene before the credits, the four main characters sit in a jail cell - strangely unfazed by what has just happened to them, still concerned mostly with the minutiae that preoccupied them beforehand. Jerry receives a page on his beeper, telling him that the plane's been repaired. He then begins a conversation about George's shirt buttons, using lines from the very first episode of the series ("The second button is the key button. It literally makes or breaks the shirt..."). George then wonders if they have had that conversation before, and they both examine that possibility. Also, Kramer is ecstatic about finally getting the water out of his ears which was the cause of the plane crashing in the first place. The camera then pans away from the group in their small holding cell, presumedly representing their self-centered isolation from society - implied throughout the show's later years, now shown quite literally.
In a last bit of comedy during the credits, Jerry is seen wearing an orange jumpsuit, performing a stand-up routine of prison-related jokes. "So what is the deal with the yard? I mean when I was a kid my mother wanted me to play in the yard. But of course she didn't have to worry about my next door neighbor Tommy sticking a shiv in my thigh." He is eventually threatened by a heckler/fellow prisoner (voiced by Larry David). The final line of the series is Jerry, being yanked off stage, saying "Hey, you've been great, I'll see you in the cafeteria!"
The rest of their adventures after that incident are unknown to all but the directors.