'Criminal Minds' Season 12 Has Major Changes Will Be Serialized! Old Serial Killer Returns

"Criminal Minds" Season 12 will include major changes as the production serialized the popular TV show. Meanwhile, Erica Messer teases that an old killer will return.

There is no doubt that things are very much different in "Criminal Minds" now after Thomas Gibson's Hotch take his departure in the series. The well-loved character has made an impression in the TV show but now, the series has to go on without him.

Buddy TV reported that the show will have a different format moving forward. Messer confirmed this by telling the publication that they are going to show a big arc in their story plot that will last in the remaining 9 episodes of season 12. The series will be serialized.

She added that a number of characters will return in "Criminal Minds" Season 12. In fact, one will be featured in the upcoming episode titled "Spencer." The intriguing character is said to be important to both fans and the BAU team.

"Oh my gosh -- if I said who (is returning), I would possibly give more away than I want to give away ..." Messer said. "But we're really acknowledging the history of the series and being able to bring back people who have made an impact, good or bad, on our characters. And we're having a really good time doing that."

Meanwhile, International Business Times reported that Messer also teases the return of an old serial killer. The culprit will strike back like Mr. Scratch and Yates. Reports have it that the story arc will be Reid-centric.

It will feature Dr. Spencer Reid (Matthew Gray Gubler) taking his mom Diana out of a clinical study. However, the next episode showed him trapped in a jail in Mexico. Who did it to him?

Could it be Cat Adams (Aubrey Plaza) or Amanda/Adam Jackson (Jackson Rathbone and Milissa Skoro) given that both killers are close to Reid? Messer is playing with the characters of "Criminal Minds" and teases that "they will be in a journey they've never been on before."

Watch "Criminal Minds" Season 12 every Wednesday at 9/8c on CBS. Stay tuned for more updates on your favorite movies and TV show.