(USA TODAY) -- Glee mourns one of its own Thursday in a tribute to Cory Monteith, who died in a Vancouver hotel in July of a heroin and alcohol overdose at age 31.
Monteith's character, McKinley High quarterback and glee-club member Finn Hudson, has died two weeks before Thursday's episode (Fox, 9 p.m. ET/PT) opens. The cause is unspecified -- "that doesn't matter," former classmate Kurt (Chris Colfer) says -- but his high-school family gathers to grieve.
The episode, titled The Quarterback, was "incredibly difficult" for all to work on because of people's feelings toward Monteith, who was "the most kind, the most generous" man, who "never had a bad word for anybody," executive producer Ryan Murphy says.
"I've never seen a crew that can't continue shooting because they've left the room sobbing. It was very hard," says Murphy, who wrote the episode with fellow executive producers Brad Falchuk and Ian Brennan. "I struggled even working on it, because what you're seeing is what they felt about not just Finn, but Cory. It's amazing performances across the board. ... Everybody went into it with a lot of love."
And several former (or occasional) cast regulars returned to pay respect, including Jayma Mays, Mike O'Malley, Harry Shum Jr., Amber Riley, Heather Morris and Mark Salling.
The episode opens with the cast singing Seasons of Love from Broadway's Rent. Among other musical highlights, already released online: The Pretenders' I'll Stand By You (performed by Mercedes); James Taylor's Fire & Rain (Sam and Artie); Bruce Springsteen's No Surrender (Puck); The Band Perry's If I Die Young (Santana); and Bob Dylan's Make You Feel My Love, sung by Rachel Berry (Lea Michele, Monteith's real-life love).
Proceeds from online music sales will benefit Project Limelight, a Canadian theater camp Monteith supported.
"It was beautiful, gorgeous," says Jane Lynch, who plays Sue Sylvester, of the tribute episode, though filming it "was a mess. Everybody was crying, but it was good. We grieved together."
Monteith missed last season's final episodes due to a stint in rehab, and this fall's openers were dedicated to a previously planned Beatles tribute, with no mention of Finn. After Thursday's tribute, the show goes on hiatus for baseball playoffs until Nov. 7.
But the young actor will be missed, Lynch says: "He was our quarterback on the set, in our Glee family, and he was the quarterback of the football team and the glee club, so we lost a big, big presence."
Murphy says he is proud of the episode, calling the performances "quite stunning," but the sense of loss remains.
"People still aren't over it," he said. "It's still very, very difficult."