Greased Lightning hits McKinley on the opening night of the musical. Santana, Rachel and Kurt return to Lima for the occasion, while Kitty steps up her vendetta against Marley.

Will and Emma's wedding is finally here, and it lands on the day of romance and love: Valentine's Day. The former and current members of New Directions reunite in Lima to celebrate.

As auditions for Grease begin, Artie hopes to cheer up Finn with the help of the returning Mercedes and Mike. Footballer Ryder Lynn is also introduced to the gang.

Rachel wrestles with her conscience when she's offered a film role that comes with a catch, leading Kurt to call some old friends to stage an intervention and stop her from making a decision she'll regret.

While Finn hopes to unite the warring New Directions by dividing them into pairs to perform duets, the Dalton Academy Warblers make their presence felt.

The Glee Club comes up with the idea of a Sadie Hawkins dance.

Finn hopes that a visit from Santana will inspire the New Directions to unleash their inner divas, while, in New York, Kurt attempts to curb Rachel's diva tendencies.

A seemingly regular day at McKinley takes an unexpected and terrifying turn when an unthinkable event has lasting consequences for the school.

While the New Directions face a crisis, Rachel receives an almost unprecedented honour and Kurt gets a second chance.

It's Christmas at McKinley and while the Puckerman brothers take steps to mend their dysfunctional family, Sue unearths some long-hidden seasonal spirit.

As everyone recovers from Will and Emma's wedding, the Glee Club is given the assignment to sing their favourite song from a movie. Meanwhile in New York, Santana makes herself at home in the loft a little too quickly for Rachel and Kurt's comfort.

Finn enlists his former buddies to help mentor New Directions through Sectionals, while in NYC, Rachel and Kurt's quiet celebration doesn't quite go to plan.

When Mr Schuester comes up with the set list for Regionals, the New Directions are not pleased. Rachel sings an unexpected song for her audition, and Marley writes an original song.

For the first time in Glee Club history, the students give the teachers, Will and Finn, an assignment to hash out the tension between them.

The members of New Directions tackle their musical indulgences, the songs and groups that everyone is too embarrassed to admit that they love.

When the power goes out at McKinley High, Will and Finn enlist the members of New Directions to 'unplug' and perform acoustic numbers. Meanwhile, Isabelle Wright asks Kurt to volunteer at the Vogue.com charity event.

The members of New Directions take on the greatest hits of music icon Stevie Wonder. Meanwhile, Artie receives news that could affect his future and his mother.

Supergirl helps Hank when a member of an alien race, who wiped out his family and his people, kidnaps Senator Crane.

Sue Sylvester finally recognises the accomplishments of Will Schuester and the glee club members, and applauds Will for setting a standard for including arts in school curriculum.

Regionals arrive and Brittany's MIT interview reaps unexpected results. Meanwhile, Rachel has one last chance to win the role of a lifetime.