Puck is oh-so-hot for teacher. All he can do is fantasize about Shelby, cue the number in which Puck plays both David Lee Roth and Eddie Van Halen.
Sue runs a smear campaign against Burt Hummel focusing on his heart attack and fabricates a baboon heart transplant. Kurt goes to Sue in protest, and Sue suggests he play dirty to win his own bid for student class president.
Shelby goes to Schue about sectionals and Schue fears the competition will turn it into World War Glee, but then Schue thinks he can channel the competitive spirit into something positive. He has the two clubs meet on the stage. Shelby and Schue sing the kids a song to bring them together. They decide to have a friendly competition by putting on a mash-up mash-off.
Puck goes to Shelby to profess his love. He tries to convince her they belong together, but she tries to dismiss his feelings as a simple puppy crush.
New Directions meets to discuss their song choice for the mash-ups and Finn nominates Rory to sing the lead. Blaine agrees it's a great idea rather than act snubbed that he's not going to be the lead. Finn tries to bond with Rory in the hall over how awful it is that Santana is trying to undermine him with her insults. When they confront the bullying singer in the hall, Finn challenges the Trouble Tones to an after school dodge ball game.
Before dodge ball, Rachel goes to Shelby and asks her for a letter of recommendation. Shelby is surprised that Rachel came to her but agrees. They speak warmly for the first time. Quinn asks Shelby is she can join the Trouble Tones, and Shelby says she needs to think about it. At dodge ball, the competition gets intense, and the Trouble Tones bombard Rory so hard with balls his nose bleeds and Kurt calls the game off. At the next meeting of the Trouble Tones, Mercedes suggests they do an Adele song at the mash-off, nominates herself president and tells Santana to lay off making fun of Finn. Mercedes gets elected team captain and Shelby agrees that the Trouble Tones need to be better not meaner.
None of this sinks in with Santana, and she goes out into the hall and delivers her meanest indictment of Finn yet to his face. Finn retaliates by saying she must be so mean because she's afraid to admit that she's in love with Brittany and that Brittany might not love her back. Santana looks hurt.
Later that night, Burt loses it over another smear ad by Sue and implores Schue to start fighting fire with fire, or else he's going to lose the race and Will will lose his job. Puck helps Shelby with Beth at her place and comes clean about Quinn's plot to get Beth back.
At the mash-off, New Directions performs two Hall and Oates songs. Before the Trouble Tones perform, we see what happened after Finn outted Santana in the hall. She's called into the Sue's office, where Sue, Burt, and Will offer to help her get counseling and Sue takes responsibility for Santana's behavior by running her own mean campaign. Santana is distraught when she finds out someone who heard Finn's hallway tirade made a video about the lesbian cheerleader, which doesn't help Sue's campaign much. Santana runs out crying.
She sings an amazing lead in the Adele mash-up and Finn whispers to Rachel that she's amazing. Santana thinks he's gossiping and Santana says he'll be sorry when everyone finds out the truth. Finn wants to know what she means, and she responds by slapping him square across the face.