‘Criminal Minds’ Season 12 Episode 4 Spoilers & Promo: Bad News For Reid; Serial Killer’s Identity Finally Revealed?

The upcoming episode of "Criminal Minds" will showcase Reid (Matthew Gray Gubler) receiving bad news about his mother Diana (Jane Lynch). The identity of the serial killer prowling Century City, meanwhile, would likely be revealed in Season 12's episode four as well.

In the exclusive sneak peek for "Keeper" obtained by TVGuide, Reid receives a call from Las Vegas police officers who informed him that the schizophrenic Diana was found wandering aimlessly around a casino. Diana was diagnosed with dementia on "Criminal Minds" Season 11 and both Rossi (Joe Mantegna) and JJ (A.J. Cook) told Reid to leave their case in the meantime to take care of his ailing mom.

The BAU team searches for a serial killer along the Appalachian Trail. First Look: https://t.co/wkd3k7w9BU #CriminalMinds pic.twitter.com/ylnk2Sy3Cx

— Criminal Minds (@CrimMinds_CBS) October 25, 2016

This latest story arc is probably preparing "Criminal Minds" viewers for Lynch's long-awaited return to her character in the eleventh episode of the current season. The former "Glee" actress last appeared in back-to-back "Criminal Minds" episodes in Season 4.

Lynch's character first appeared in the long-running police procedural crime drama's Season 1 finale, Parent Herald previously reported. Reid first knew about Diana's dementia in "Criminal Minds" Season 11, saying that she didn't recognize him immediately upon seeing her son.

It was also in that season when Reid took a vacation in Paris along with Diana, who appears to be doing fine back then. "Criminal Minds" showrunner Erica Messer teased that Lynch's return will introduce a "heavy Reid story."

Episode four of "Criminal Minds" Season 12 will showcase Emily Prentiss (Paget Brewster) leading the Behavioral Analysis Unit (BAU) team to hunt the serial killer along the Appalachian Trail in the outskirts of Virginia. The serial killer's identity is still unknown but his/her right arm was seen in the promo covered with coagulating blood. This suggests that the killer will be difficult to recognize at first and he/she might have a wild or abnormal nature.

Meanwhile, episode 13 of "Criminal Minds" will be co-written by Messer and Kristen Vangsness. The episode is guaranteed to be big, Parent Herald previously reported.

"Criminal Minds" airs episode four today, Wednesday at 9/8c on CBS. How will Reid handle his sick mother? Will the BAU team succeed in apprehending the loose serial killer? Share your thoughts and watch the exclusive sneak peek below.