For a class project for the man-hating science teacher, Ms. Barch, Daria is paired with jock Kevin (who is more interested in watching football on the Morgendorffers' TV than working with Daria) while Brittany works with resident pervert, Upchuck, who blackmails her under his command.
At Lawndale High, during science class, Janet Barch presents a lesson on acquired behavior involving a lab rat, interspersed with comments regarding her hatred of men and the recalling of how her husband left her. Ms. Barch's dislike of males extends to her male students but she praises Daria’s morbid answer to a question on reinforcement.
She concludes the lesson by assigning teams of students for a home science project consisting of training a rat to run through a maze. Because of her morbid comments, Daria is paired with Kevin so he can suffer; and Brittany is paired with Upchuck. (Brittany ends up sobbing in the toilets) Daria isn't sure how to get out of Kevin 'helping' her until he asks if they can work at her house, because his cable TV isn't working.
That evening at the Morgendorffers, Helen asks Daria about her upcoming project, partly to avoid hearing about Quinn's day. Helen ignores Daria’s comments on Helen's lack of sincerity and comments that associating with Kevin could help Daria socially: something that leaves Quinn aghast. Quickly, Quinn says she could help too! Kevin arrives shortly afterward and Daria distracts him from the project by turning on the Pigskin Channel, while she retires to the garage to work on the project alone. Quinn attempts to flirt with Kevin, seeing a way into his social circle, but Kevin is completely oblivious: an attempt to get him to fetch a soda gets the response "thanks babe, can you put some ice in it?"
Meanwhile, Brittany has arrived at Upchuck’s house under a heavy disguise. She warns him not to get ideas about her presence and rejects doing work, but Chuck has blackmail material: a photograph of her and Oakwood High's quarterback in a compromising position. Chuck then changes his mind, and decides he'll do the maze and blackmail Brittany into doing chores and favors for him. He chuckles to himself that she will be his slave for a week.
A few days later, Daria has finished the maze and trained the mouse. Kevin continues to watch football in the TV, oblivious to strong hints that Kevin should go out with her, while Quinn shuts out Brittany so she can't interfere. Kevin eventually goes to the garage (he got lost), breaking part of the maze by accident, with Quinn following in order to offer him a massive chocolate layer cake. Kevin tells Quinn to leave the caked by the TV and remarks that it's like they are already going out.
Kevin and Daria are surprised by Brittany, who quickly deduces that Kevin hasn't been working and manipulates him into admitting by asking him to explain the project to her. Kevin nervously tries to explain their project, however Brittany still does not believe he's been working, and thinks he must have been seduced by both Morgendorffer sisters. Daria happily furthers this belief, and Kevin doesn't help his case by not wanting to leave. He states that it's only half time in the game he's watching but then catches himself, saying that Daria needs him. The cheerleader warns Daria that she will fight for her man, and Kevin wants to know what man she's referring to.
The following night, as Daria and Jane are discussing the project at Pizza King, they are interrupted by Kevin, who wants to arrange another visit to watch the Steelers game. He remembers he promised to help Quinn "with her back massage technique"; their fellow students are watching and listening, including the Three Js. They've noticed that Kevin has spent every night that week at Daria's, and Jamie White figures there must be something 'good' about Daria that they'd unaware of. A watching Brittany steps in to get Kevin to take her on a date to see the new Whitney Houston movie, only for him to try and claim he needs to work; Daria tries to get him to take the night off, causing an angry Kevin to stage-whisper that he wants to avoid the "chick movie." He's caught out by Brittany and flees.
The jealous cheerleader tells Daria she can't steal "my Kevvie" because "you're a brain." Daria agrees this is "a very astute observation about the likelihood of me dating your boyfriend," only for Jane to question if it should be former boyfriend. The situation is made worse when the J's come over; Brittany tries to pick them instead but they brush her off in order to ask Daria on a date (until Quinn comes along and they revert to type).
Brittany wails to a fed up Jodie that she can't compete with sisters but when Jodie snaps "maybe you could get your brother to wear a skirt", the cheerleader gets an idea (but it'll have to wait until after she's done Upchuck's shopping). Later that night, while Quinn tells a friend over the phone that she's "kind of dating" Kevin and juggles her dates, Brittany gets into the garage, using the grand cover story of "Kevin wants this, can I leave it in the garage?" She kidnaps Daria and Kevin's mouse, the 'excuse' for the sisters to 'steal' Kevin. She leaves the mouse in her psychotic brother Brian's (lack of) care.
Discovering the missing mouse, Daria informs Kevin. Then, she explains to Kevin that this will mean they'll fail the assignment. Kevin wishes there was something he could do..."but what?" Then he just sits and watches the Pigskin Channel anyway. Jake Morgendorffer attempts to do male bonding with Kevin, which turns into a bitter rant about military school and how he likes to think all his classmates died in the Vietnam War and the shame of masturbation. Kevin isn't listening to Jake's ramblings. While Quinn tries and fails to distract Kevin from the TV with a short skirt, Daria quizzes her and finds out that Brittany has stolen the mouse.
The next day at school, Kevin protests he hasn't done anything wrong and discovers for the first time that everyone thinks he's dating Daria and Quinn. He's actually quite happy about the rumor because he thinks Daria and Quinn are twins. Daria is able to trick Brittany into exchanging the mouse for Kevin, claiming that Barch is going to make her and Kevin do a make-up experiment that could take weeks. Both Brittany and Daria think they've won that deal, each thinking the other is a sucker, while Kevin wants to know if he can still go to Daria's house to watch the Pigskin Channel. Brittany quickly tells her parents to get cable. Quinn is distraught at losing access to Kevin, while Jake's neediness makes her think he's after Kevin too!
Unfortunately, Brian's treatment has left the mouse traumatized and worthless for the project. The next day at school, Daria uses Brian's abuses as an example of negative reinforcement and plays on Barch's anti-male neuroses, and earns a top grade—while Kevin, who had been mute and striking poses during Daria's speech, barely receives a passing grade (which he still considers cause for celebration). Meanwhile, Upchuck gets an F despite all his work because Barch will only let girls give the presentation, and Brittany knows nothing because she was too busy slaving for Chuck to do any work. After class, Kevin tells Daria he really liked hanging at her house. He tells her there's a big party at his house on Friday, and asks if Quinn can make it.