In this conclusion of the long running series it finally happens: Kelly and Zack will marry. Zack's parents are against the early commitment and Kelly's parents can't afford it, so only the gang travels to Las Vegas for the wedding. However, before the wedding can happen, they have to live through many adventures, including Zack losing his hard earned money, Kelly becoming jealous and Slater being chased by mobsters.
Zack arrives at California University expecting to be sharing a room with Slater and a suite with three girls. He accidentally goes into the wrong room. Two girls come in as he is stretched out on the bed; another comes in as they are teasingly arguing about whose room it really is. They introduce themselves as Alex Tabor, Leslie Burke, and Danielle Marks. Alex thinks Zack is cute, but Leslie is not too impressed. As Zack and Slater settle into their room, Screech arrives. He has arranged to be sharing their room as well. Later on Leslie walks into their room as they are all standing around in their underwear. Zack is visibly embarrassed, but pretends not to be as Leslie taunts him just a little. The suite mates all have a meeting about how to decorate their common room. Mike Rogers, the resident advisor, comes in with a list of rules and warns them not to break them. One rules is no parties during the week and another is no alcohol on the premises.
Zack convinces Leslie to go out with him. After their date, Leslie tells him that she thinks they shouldn't see each other because they are roommates and because she doesn't want to be the flavor of the week. He gets sympathy from her by telling her of his lost love, Kelly, who died in a boating accident. As he's showing Leslie a photo of Kelly, Kelly walks in. Surprise! She's just transferred to Cal U. and Screech has arranged it so that she will be the new roommate, in place of Danielle who transferred out. Leslie is disgusted.
Zack gets off on the wrong foot with his new professor of anthropology, Professor Lasky. Professor Lasky pegs Zack as a smart mouth immediately and turns the tables on him by selling him a copy of the midterm before Zack realizes that he is the instructor. All the girls have crushes on Professor Lasky, while Slater is trying to gain weight so that he can wrestle in a higher weight class.
Slater is being courted by an exclusive fraternity while Leslie is being courted by a sorority. Zack really wants to get into the same fraternity as Slater, but they don't seem as interested in him. Zack pretends that he plays hockey in order to impress Rick the fraternity guy, but it turns out that the Rick plays hockey also, so Zack has to go to the tryouts.
Zack wants to take Leslie on a ski trip, however, she won't go alone with just Zack. Zack asks Slater to go along, so he must find a date to bring along with them. Slater meets a girl who challenges him to become more interested in his heritage. His involvement with a group that wants the university to institute a Chicano studies program forces him to cancel the ski trip.
It's homecoming weekend. Leslie's parents come to visit her. She is sick of their controlling ways, so she asks Screech to be her date in order to freak them out a bit. Screech agrees to be especially geeky for this event. He does a good job of freaking them out, but eventually they figure it out and they agree to back off and allow Leslie to make some of her own decisions from now on.
Zack, Slater, and Screech make plans for a Friday night poker game. Mike nixes the idea of having the game and the guys decide to help him with his love life to get Mike off their backs. They encourage Mike to ask out the English literature professor, Judith Trudell, that he has a crush on.
Zack is not paying attention in anthropology class so Professor Lasky asks him to his office for a talk. While Zack is there, Professor Lasky steps out for a few moments and a beautiful blonde steps in. Her name is Jennifer, and she is looking for Professor Lasky. Zack says that he is Professor Lasky, and makes a date with her.
Zack begins dating a tennis star, Linda. He is at least partly intrigued by her fame. She is struggling with astronomy so Zack gets Screech to tutor her. Linda continues to date Zack, but she and Screech are enjoying their time together. Zack notices and he and Screech have an argument about it. Screech temporarily moves in with Mike and drives him crazy.
Kelly is thinking about becoming a doctor. Zack discourages her, and Kelly begins to give up her dream. She begins skipping some of her classes and gets a job at Skeeters as a cocktail waitress. In the end, Zack realizes he was wrong and tells Kelly that she shouldn't give up her dreams for anyone. When she discovers she's aced her chemistry test, she gets back on track. Meanwhile, the guys help Mike prepare for his tryout for a comeback to the NFL. He succeeds, but decides not to play. He's put too much time into getting his graduate degree, and he feels needed there at the school.
When Thanksgiving plans fall apart, the gang helps Rogers prepare a meal for underprivileged kids.
Since Kelly fancies Professor Lasky, she goes to his office to supposedly discuss a paper she has written. She finds him there with his child and offers to babysit. Lasky and Kelly grow closer and closer and at the end of the episode Lasky and Kelly share a kiss.
Although he is jealous, Zack reluctantly agrees to help Kelly and Professor Lasky keep their relationship secret, since it is against the rules for the teacher to date one of his students. However, after Kelly drops Dr. Lasky's anthropology class, Zack becomes worried about her, and reveals the relationship in front of the entire class. However, since Kelly is no longer one of Dr. Lasky's students, this seems not to be particularly problematic. Kelly and Dr. Lasky continue to date, but Dr. Lasky does not want to be seen or recognized with her. She does however get him to agree to escort her to a masquerade ball. Meanwhile, Mike Rogers gets Screech, Slater, Alex, and Leslie take a "Perfect Mate" quiz which suggests that Slater is perfect for Leslie, and Screech for Alex. This makes Alex very upset, especially when Slater and Leslie independently decide to attend the masquerade ball as Tarzan and Jane. At the last moment, Slater asks Screech to switch costumes, so that he can accompany Alex's Tinkerbell in Screech's Peter Pan outfit. At the party, they discover the girls have had the same idea: Alex and Screech are stilled paired up as Tarzan and Jane, and nobody is wearing the costume they want. After Kelly becomes enraged at Zack for betraying her trust and revealing the relationship, Zack decides that the best way to get Kelly to come near him is to go to the costume ball in the same Zorro costume as Dr. Lasky. This works perfectly: at the ball, she mistakes him for Dr. Lasky and they kiss. When she finds out she kissed Zack, she is understandably upset. But this turns out to be the least of her problems: at the ball, Dr. Lasky gently breaks up with Kelly; he is tired of being afraid to be seen all the time, and the age difference is not helping. Back at the suite, Screech tells Alex that the tests mean nothing, and what the couple went through for each other with the costume fiasco proves they belong together. Alex agrees and makes up with Slater. In Kelly's room, Zack tries to comfort Kelly by telling her he loves her. While she is no longer angry at him, she tells him she just wants to be good friends. After she leaves, Zack tells the audience that they are good friends for now, but that he will win her heart.
An Ethics course with a tough professor, drops a midterm paper which Zack picks up and reads. Lesley takes it off him and tears it up.
Zack and Slater start a rave to raise money so they can take Alex and Kelly to Cancun.
Zack gets a job at the health center to get close to Kelly. Unfortunately, Professor Lasky winds up there as well, and Zack has to come up with one scheme after another to get him out of the way.
The gang is shocked by the death of a popular teacher. Meanwhile Zack takes desperate risks to get Kelly to say that she still loves him.
Just as Zack and Kelly are getting pretty close, Kelly is accepted to the Semester on the Sea program, which involves a three-month cruise. Zack doesn't want Kelly to go, but she feels it's an opportunity she can't pass up. Zack tries to get accepted into the program as well, but none of his schemes work. He tries to get Screech to quit the program by scaring him, but that backfires.