While Screech hides a lab monkey destined for the zoo, Zack discovers Kelly's crush on Professor Lasky.

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.

With Mike gone and in need of money for a trip to Cancun, Zack and the gang stage a rave in the dorm.

With Kelly still pining over Professor Lasky, Zack tries to find ways of getting her attention and ends up volunteering as an orderly at the health center. 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. Meanwhile, Screech tries to fit in with a group of pledges at his fraternity.