Glee sources tell us that Finn (Monteith's character) would have been in the final two episodes of the season had he not checked into rehab, which means storylines now have to be changed. We hear the writers are finding an organic way to handle his absence, as when his character joined the army at the beginning of season four. The season finale will revolve around New Directions competing at Regionals, and production is set to wrap no later than April 24.
"Most of the cast didn't know there was any problem and many of them are surprised," a show source says. "Everyone seems to support his decision to get help and to not delay it."
As for his relationship with costar Lea Michele, they are "as strong as ever," according to another source close to production. "There haven't been any hints of trouble."
Monteith has been has struggled with drugs in the past. In an interview with Parade, the Glee star admitted that he had a "serious problem" as a teen, and that when he quit at age 16 he was "lucky to be alive."