The highly anticipated episode 4 of "Criminal Minds" season 12 has been cancelled on October 19 to give way to the final presidential debate of Donald Trump and Hilary Clinton. That means the fans of the series will have to wait a little longer for the telecast of "Keeper," which follows the BAU team as they deal with a monster creature.

According to reports, "Keeper" is a Halloween-themed episode that features a mysterious serial killer responsible for the gory murders in Appalachian Trail. The killer has already slain seven people in the trail, which is a remote part of Virginia.

The investigation on the gory murders will see the return of former Bahavioral Analysis Unit member Emily Prentiss, portrayed by Paget Brewster. In the episode, she will help Aaron Hotch to investigate and track down the murderer. The investigation is expected to be suspense-driven, leaving the entire search operation team baffled as they try to figure out the modus of the killer.

While the BAU does its best to crack the case, the truth about the identity of the killer is revealed. Viewers of the series will know if the killer that they are dealing with is simply a monstrous human being or a non-human creature.

In other news, one of the most beloved characters in the series, Aaron Hotchner, will no longer be part of the series. Played by actor Thomas Gibson, the character had to be written off after Gibson had an on-set altercation with one of the show's producers.

"Criminal Minds" season 12 returns on October 26 on CBS.