"Gut-wrenching" and "so, so good."

We've talked to sources who have read the script for Glee's Cory Monteith tribute episode, which is scheduled to begin production today in Los Angeles, and by all accounts, it does not disappoint.

"You will cry from beginning to end," says one insider.

"I cried as I read it, on every page," says another.

No spoilers here, but we can tell you that the episode takes place in Lima, Ohio, and centers around the death of Cory's character Finn Hudson. As promised, it is not revealed how Finn died, but the episode starts off with the news of his death and then moves on to focus on all the characters remembering and mourning him, and celebrating his life.

We are told that Lea Michele (Rachel) does not appear in the episode until the final act. Her presence is limited but incredibly powerful. And yes, she does sing.

We can also tell you that Santana (Naya Rivera) has a great, memorable part in the episode.

And the final song? Get ready to ugly cry.