On the fourth season finale of 'Glee,' the New Directions head to Regionals to take on their new competition (which includes 'American Idol' Season 11 runner up, Jessica Sanchez) and try to clinch the trophy for the third year in a row.

Brittany (Heather Morris) is at MIT for an interview. After telling her she scored a zero on her math aptitude test, they ask her what the numbers she scribbled on the back of her test are. She explains that her head was full of numbers and she just needed to get them out. They explain to Brittany that she wrote down a huge prime number that a normal human shouldn't be able to find on their own. When read in various other directions, the numbers are math theorems found in quantum mechanics and they tell Brittany she's the greatest mind since Albert Einstein. They then tell her they have an unheard of proposition for her.

Ryder (Blake Jenner) is still trying to figure out who has been catfishing him as the imaginary Katie when Mr. Schuester (Matthew Morrison) tells the glee club that Regionals have been moved to their school. He then tells the kids to send good vibes to Rachel (Lea Michele) who is about to have her final callback for 'Funny Girl' in New York.

At the audition, Rachel performs Celine Dion's 'To Love You More.' A crying Rachel finishes the song and she's told that they'll let her know the outcome.

Blaine (Darren Criss) talks to Sam (Chord Overstreet) about his plans to propose to Kurt (Chris Colfer). Sam thinks it's too early and Blaine says he will do it with or without the person he wants to be his best man.

Britany enters the glee room to tell the club that she wants to sing all the solos from now on or she's out. When Sam tells her she's out of line she breaks up with him via text message and leaves, saying that for her it's now all or nothing.

Coach Roz (NeNe Leakes) opens her office door to find Brittany nailing a paper on her door with 95 reasons why she's quitting the Cheerios. She then lights her uniform on fire.

Ryder says he won't perform at Regionals unless someone admits they are the person catfishing him. Things come to a head when he orders everyone to take out their phones and Marley (Melissa Benoist) says it was her all along. When Jake (Jacob Artist) defends her, saying it was just a joke, Ryder leaves in a huff.

Tina (Jenna Ushkowitz) is helping Blaine pick out an engagement ring when a friendly shopkeeper named Jan (Patty Duke) talks to him about her relationship with her own girlfriend after hearing that Blaine is gay. Sam arrives out of the blue to help Blaine, but Jan takes him aside and asks him if he has like-minded friends who are in a similar situation.

Brittany is accosted by Sue (Jane Lynch) and Will who want to talk to her. Brittany will only talk on her terms, so she brings them on her web-series Fondue for Two and reveals through various evidence that the father of Sue's child is Michael Bolton. Apparently he owed her a favor for once saving his life.

While Brittany is occupied, Sam calls Santana (Naya Rivera) and says he needs her help with Brittany.

Jan takes Blaine and Kurt on a double date with her longtime girlfriend Elizabeth (Meredith Baxter) and they explain to the two boys what it was once like to be living in a much less gay friendly world. After stepping around how she met Blaine, Jan proposes and Elizabeth says yes as everyone in the restaurant applauds.

Marley approaches Ryder and asks if they can talk. She tells him they need him for Regionals and when he asks her why she did it, Unique (Alex Newell) interrupts them and says it was him all along. After thanking Marley for covering, Unique says she got in too deep and couldn't admit to lying to Ryder because he "didn't want to lose" what they had. An angry Ryder retorts, "We don't have anything" and tells Unique he will never speak to him again.

Santana visits Brittany, who tries to force her on Fondue for Two. When Santana says she wants to know why Brittany is acting different, Brittany replies that what she has to say will change everything.

Emma (Jayma Mays) arrives at Regionals to cheer the kids on and Ryder arrives in the back to help out. He tells Will that even though he's helping out during Regionals, he plans to officially leave the glee club afterward.

The Hoosier Daddies, led by Jessica Sanchez perform Zedd's 'Clarity' and 'Wings' by Little Mix. As they finish, we see Brittany enter the audience and hug Sam.

Inside the glee room, Brittany tells everyone that she got early admission to MIT and they want her to leave immediately - hence her sudden severing of ties. She admits that all her life she felt stupid until she joined glee and it let her believe in herself. She says her tearful goodbyes to everyone and they share a group hug before heading out to perform.

Onstage, the New Directions sing and dance to 'Hall of Fame' by the Script (featuring will.i.am), Icona Pop's 'I Love It' and Marley's original song 'All or Nothing.' Their performance receives a standing ovation.

After a few tense moments, the Hoosier Daddies are given second place and the New Directions are once again awarded first. Everyone celebrates and in his excitement, Ryder even hugs Unique, although they both appear uncomfortable about it.

Later on, Brittany sits on the empty stage when she's joined by Santana. They walk off hand in hand.

As Will is cheering on their win and saying that Nationals is only around the corner, Emma walks in with a priest. She and Will announce they're having a surprise wedding to take the pressure off her. The kids hum an impromptu bridal march and Emma and Will exchange heartfelt vows and they are pronounced husband and wife.

Behind his back, Blaine fiddles with a black box which we're led to believe contains an engagement ring.