Just last season, Reid took a leave of absence to go visit his mother after she’d taken a turn for the worst.
The two then took a vacation to Paris that fans can expect to be referenced in the Season 12 opener.
Reid’s mother is very important to him, and, as such, Diana has been mentioned several times over the years.
Criminal Minds executive producer Erica Messer told TV Guide that a big Reid centric story is coming up for early next year, and that’s why Diana will finally show up again.