"Criminal Minds" Season 15 will be the last time fans are about to see their favorite Behavioral Analysis Unit (BAU). It is not yet revealed what cases these behavioral profilers have to face in its last season, but someone is set to be back.

Fans are expecting "Criminal Minds" Season 15 to tie all of the series' loose ends, and it may finally happen with the appearance of Reid's (Matthew Gray Gubler) mother. CinemaBlend reported Jane Lynch revealed she would be back as Diana Reid in the final season of the police procedural crime drama.

"Having a day for myself," Jane Lynch said in a Twitter post. The 58-year-old star shared what seemed to be a photo of "Criminal Minds" Season 15's filming with a director's seat, bearing the show's title.

Jane Lynch didn't reveal her storyline in "Criminal Minds" Season 15, but fans are expecting that her appearance will be an emotional ride for Reid. Diana's health has deteriorated over the years. She was even diagnosed with dementia, which made her realized she could forget her son at any moment.

Fans last saw Diana in Season 12 finale when Reid's enemy held her hostage. Now that she would return to "Criminal Minds" Season 15, showrunner Erica Messer told TVLine her appearance has something to do with the big revelation in the Season 14 final episode. "It's a really beautiful way to bring them back together," she said about the mother-and-son reunion.

Meanwhile, Messer also discussed why "Criminal Minds" Season 15 is the perfect time to end the series. She revealed that the time she found out about the cancellation, she had enough time to write a proper season finale. She even knew they would have 10 episodes to wrap up the series. 

Although Messer admitted there is an "endless supply of stories to tell," they are still in business, and "Criminal Minds" Season 15 will be their end. It is enough for her that people have invited them into their living rooms since 2015, and they have treated them with incredible respect.

Messer knew it was the end of the series even before Season 14 wrapped up its filming. She told Entertainment Tonight that learning "Criminal Minds" Season 15 would be the end of the series let her "do an ending to the season that didn't have to conclude the entire show."

"Criminal Minds" Season 15 would give the show a satisfying ending. But before this happens, the Season 14 finale would focus first on Rossi's (Joe Mantegna) wedding, and the danger Reid and JJ (A. J. Cook) have to face.