Will announces his sabbatical from McKinley to the glee club, revealing that Finn will replace him until he returns - after Sectionals. Sue summons Will and Finn into Figgins' office. She objects that Finn doesn't have the credentials or maturity to oversee the glee club, but Figgins and Will agree that Finn's simply an adult volunteer. Furious, Sue insists that if Finn remains in charge, her fragile peace with the school will be over, and she storms out in a destructive rampage.
Rachel tells Brody she's landed her first off-Broadway audition, but Cassandra warns Rachel from her own experience that the director will eat her alive - she doesn't think Rachel's been hurt enough in life to make the cut. Determined, Rachel encourages Cassandra to try out too, "to get back in the game." Cassandra offers Brody a teaching assistant position, and he accepts but puts off starting until after he can help Rachel prep her audition.
The glee girls get their "Grease" wardrobe, and Kitty insinuates that Marley's inheriting her mother's weight problems when her Sandy costume doesn't fit - but Kitty had secretly altered the costume beforehand. Claiming a desire to win new friends, Kitty invites the girls to a sleepover.
Marley asks her mom about her weight gain, concerned about a genetic connection, but her mother gently reminds her that even if that's true, Marley can choose her own course: "I didn't raise a victim or a quitter - I raised a star. You have control over your life and your body." They agree to a strict diet together.
Finn attempts to apologize to Sue for his insensitive remark about her baby. Sue refuses to accept, claiming she's seen his true colors and believes "you have hate in your heart." To frustrate him, she's reserved the auditorium for Cheerio practice, forcing Finn to find a new rehearsal space. Finn brings the guys to Burt's auto shop to get into character as grease monkeys and better understand the musical's themes: fixing cars, getting your hands dirty and bonding forever with your friends. They're soon perfecting "Greased Lightnin'."
Kurt's tempted to return to Lima for the musical, but neither he nor Rachel are sure it's the right thing to do after their fractured romances with Blaine and Finn. Overhearing, Cassandra urges them to go to get closure or to simply just have fun - she even offers them her own frequent flyer miles.
At the sleepover, Kitty mercilessly trots out donuts, and seeing Marley's panic, she takes her aside and not-so-subtly suggests that Marley should try a binging-and-purging approach. As Marley considers it in the bathroom, Kitty mocks her to the other girls with the "Look at Me, I'm Sandra Dee" routine from "Grease."
When Wade/Unique's parents learn about his Rizzo casting, they worry about his safety. Although they've been supportive, Sue fans their fears by revealing bullying incidents involving Wade. The Adamses pull Wade from the musical and require him to dress as a boy at school. Tina takes a crash course in the Rizzo role but is irritated to discover that Finn has recruited Santana to take on the part she was "born to play."
Rachel and Kurt nervously return to McKinley, finding themselves awkwardly facing both Blaine and Finn. Finn assures them he's happy they came, but there's weirdness. Kurt thinks they've made a mistake in coming, and tortured looks are exchanged during Blaine's onstage performance of "Beauty School Dropout."
Marley's ever-tightening wardrobe prompts her to seriously consider Kitty's advice. Ryder finds her gagging herself in the bathroom. He tells her about his second cousin, a college wrestler who tried to drop weight through extreme diets, purging and laxatives. Rather than ending with his cousin dying, Ryder instead reveals that his relative had a particularly embarrassing incident on the mat. Easing the tension, he tells her, "I don't want to kiss a girl who's got puke on her breath - onstage or later." Marley reassures herself with the "Sandra Dee" goodbye refrain from "Grease."
As Santana performs Rizzo's showcase song "There Are Worse Things I Could Do," Wade suffers watching from afar, and the lyrics are mirrored in Cassandra's determined seduction of Brody during their training session. Meanwhile, wowed by Tina's performance, Mike wants to reconcile, and while Tina admits she was tested by the breakup, she's interested in talking about it.
Marley's confidence takes another hit after Kitty reveals that a merciless theater critic is in the audience, and Ryder boosts her back up with a passionate kiss - one that doesn't escape Jake's notice. Their performance of "You're the One That I Want" prompts Rachel to fantasize she and Finn are singing the leads - in fact, ALL the glee club's fractured couples imagine dueting with their ex-loves. But when Rachel calls Brody, Cassandra answers the phone, cruelly spelling out how she set out to teach Rachel a lesson about overreaching.
Finn spots Rachel after the show, realizing she's been crying - the type of tears she reserves for guy trouble. Upset that she no longer cries over him, Finn insists that they should have no contact whenever she returns to town, and Rachel agrees, telling him, "This doesn't feel like home anymore." Blaine and Kurt also have a confrontation, with Kurt rejecting Blaine's appeal because he doesn't trust him anymore.
After positive reviews for the show, Will's pleased to leave the glee club in capable hands, but as he says goodbye to Finn, he tries to offer some final advice. "I've got this," the newly confident Finn assures him.