Glee cast members will come together later to pay tribute to their co-star Cory Monteith in a special send-off.
The third episode of the fifth series - The Quarterback - is dedicated to the 31-year-old actor who was found dead in a Canadian hotel room in July of an accidental alcohol and drug overdose.
The McKinley High School family of past and present will join together to remember and celebrate the life of his character Finn Hudson.
The show's creator Ryan Murphy has not disclosed any details of the episode.
However, a 30-second trailer has been released and sets a sombre tone for fans.
It opens to a weeping Rachel Berry, the character played by Monteith's off-screen girlfriend, Lea Michelle, being comforted by glee club teacher Will Schuester, played by Matthew Morrison.
She is singing Bob Dylan's Make You Feel My Love in the background, as the words "the hardest word to say ... is goodbye" appear on the screen.
The footage also shows a memorial display featuring Finn's football helmet and a wooden figurine wearing the No 5 jersey, surrounded by students, as well as the quarterback's locker.
Other songs in the episode include covers of Seasons Of Love from the Broadway musical Rent, James Taylor's Fire & Rain, The Pretenders' I'll Stand By You, The Band Perry's If I Die Young and Bruce Springsteen's No Surrender.
Mike O'Malley, who plays Finn's stepdad Kurt Hummel, said: "He dies of cancer, in a car accident, he dies of old age, he dies because of a drug overdose. It doesn't matter.
"He's gone and you're never going to see him again, and so now you gotta go to work, you got to honour his life, you're trying to honour his fans' relationship with the character."
He said the episode included "the most emotional scene I've ever acted in my entire life". and described Monteith as "a real bright light".
:: The Quarterback airs at 9pm EST (2am GMT) on Fox. Glee is shown on Sky 1 HD, Fridays, 8pm.
