After Jeff passes his history course, Annie and the rest of the group realize he's reached his requirements to graduate early. Jeff plans to begin his now legitimate law career back at his old firm, but not before the gang throws him one last, epic graduation party.
Dean Pelton and Annie have assumed responsibility for Jeff's blowout graduation party. But in private, Jeff tells Britta he's worried a big soiree celebrating his departure will be tough on the rest of the group emotionally, specifically Abed. Britta tells Jeff not to worry; Abed's been making huge strides ever since his "darkest timeline" incident a few months back. Later, in the study room, Jeff changes his tune about the party and suggests they roll a dice to decide who brings the soda to the event. But when the dice lands on its side and not on a number, Abed leaves the room, hoping they haven't reopened the portal...
In Dean Pelton's office, the Darkest Timeline opens up and Evil Jeff appears, ready to wreak havoc on the plans of his more placid counterparts in the present, more docile timeline. Evil Jeff meets up with Evil Annie, and the two scheme to ensure his "boring alter ego" graduates and takes his awesome job at his old law firm. In the study room, Evil Jeff finds Normal Annie and flirts with her. This unusual change of pace is enticing to Annie, who's always had a thing for Jeff. But when Evil Jeff ridicules her "high school" lifestyle at Greendale and rubs his graduation in her face, Annie sulks away with her feelings hurt. In the cafeteria, a crying Annie finds Boring Jeff and tells him off, much to his confusion.
In the hallway, Abed runs in to Evil Jeff and recognizes him right away. When Evil Jeff shoots Abed with an evaporating paintball gun, Abed disappears and regenerates in Dean Pelton's office, where he quickly realizes the Darkest Timeline has infiltrated the present. Abed retreats to his apartment, where he finds Evil Abed, though his doppelganger assures him he's given up the nefarious lifestyle for nobler aspirations. Together, Abed and his evil version plot to defeat Evil Jeff and save the present timeline.
In the library, Boring Jeff finds Annie and apologizes for whatever it was he did that made her cry. She apologizes too, claiming his impending graduation has been too much for her to handle emotionally. Boring Jeff is glad that fire has been extinguished - unfortunately Evil Jeff is busy setting more relationships ablaze. In the cafeteria, Evil Jeff "un-vites" Troy and Shirley from his party and seizes the opportunity to ridicule both their lives. Troy and Shirley are broken by Evil Jeff's cruel words.
Evil Jeff and Evil Annie confront Boring Jeff and demand he go through with his graduation and leave Greendale once and for all. But Boring Jeff is apprehensive about abandoning his study group - he's grown so much over the past four years and likes who he's become inside the walls of this institution. Evil Jeff has had enough of Boring Jeff's banter and decides to blast him into oblivion with his evaporating paintball gun, but as he shoots his weapon, Chang comes out of nowhere to take "the bullet" for Boring Jeff. Boring Jeff escapes just as Evil Shirley, Troy and Britta show up to take out their passive counterparts once and for all.
Normal Shirley, Troy, Britta and Annie are furious with Jeff for his recent rude behavior and boycott his ceremony. Jeff shows up to tell his friends about the Darkest Timeline, but this only infuriates them more. Get real, Jeff! But when Abed confirms Jeff's story and arms his friends with evaporating paintball guns of their own, the group realizes the gravity of the situation and agrees to take their evil doppelgangers out before they have a chance to return the favor.
The normal version of the study group butts heads with the Darkest Timeline in the school cafeteria, and a knockdown, drag-out, paintball-warping gunfight ensues; whichever version shoots their other selves first, wins. When only Evil Jeff remains, Abed finds Boring Jeff behind a couch and reveals the whole thing is just a figment of Jeff's imagination. Jeff has created this alternate universe in his mind to delay confronting his departure from Greendale. Finally taking responsibility for his life, Jeff stands up and evaporates his evil self, which suddenly brings him rushing back into the present moment.
The study group is still sitting around waiting to hear Jeff's word on whether they can throw a party for him. Jeff tells the group that as long as they are at his ceremony, that's all that matters to him. At the ceremony, Jeff takes the time to tell the gang how much they've meant to him. His love for them is immeasurable, even when you split it seven ways. Jeff graduates and decides to join a small local firm, that way he can use his big mouth to help the "little guy" and also still be close enough to stop by to see the study group whenever he misses them.