"We're really excited. It's a fun Reid story and she's really excited to come back and reprise her role," Messer says. "She's been a busy lady and we're still here, so we're happy to be able to offer that opportunity for her to come back."
Lynch last appeared as Reid's schizophrenic mother in November 2008, a year before Glee premiered. Her subsequent short-lived sitcom Angel From Hell also prevented her from returning to Criminal Minds. In May, Messer told TVGuide.com that the "stars are aligning" to finally get Lynch, who's unattached to a series for the first time in seven years, to return. "I would love, really more than anything, if we could get her this year," she said.
Diana's absence, of course, didn't stop the show from mentioning and giving updates on her. In Season 9, Reid received a postcard from his mom about her supervised trip to the Grand Canyon. And last season, Reid took a leave of absence to visit her at Bennington Sanitarium after she took a turn for the worst. He later revealed, during a cat-and-mouse hostage situation, that his mother has onset dementia and didn't recognize him right away. However, she was doing better by the finale, when Reid was planning a trip with her to Paris.
"They did take a trip together. We learn about their trip to Paris in the premiere. Reid talks about that," Messer says. "[Her return] will be good. That's why everybody's excited. It was more important than ever to have Jane come guest-star because it will be a big story."
Season 12 of Criminal Minds premieres Wednesday, Sept. 28 at 9/8c on CBS.
(Full disclosure: TVGuide.com is owned by CBS.)