‘Bones’ Season 11 Finale: Brennan, Booth face new serial killer linked to first season [Spoilers, Review]

“Bones” Season 11 finale, titled “The Nightmare in the Nightmare” (Bones 11x22) airs this Thursday, July 21, on Fox. Showrunner John Collier has revealed Jeffersonian’s Temperance Brennan (Emily Deschanel) and FBI’s Seeley Booth (David Boreanaz) will encounter a new villain, the Puppet Master, whose history is related to the first season of the show. Boreanaz himself directed this special episode.

Spoiler alert: This update contains more “Bones” Season 11 spoilers. Fans are now guessing who the Puppet Master is. He or She seems to know a lot about the Brennan and her entire crime-solving team. If he or she is linked to Season 1, could it be Zack Addy (Eric Millegan)? Watch the Bones 11x22 promo video below.

“We are going to be seeing a type of serial killer we've never dealt with before,” Collier told E! News. The show boss also dropped an intriguing clue. “We're going to bring in a new threat, a new villain, who couldn't have existed if the first season hadn't existed.” He added, leaving fans with something to think about: What are the key events in “Bones” Season 1?

‘Bones’ Season 12 is final season with 12 only episodes

By connecting “Bones” Season 11 finale to the freshman year of the crime dramedy, Collier pointed out the show is going back to its roots. This makes sense as the series is getting ready to wrap up with its 12 final episodes.

In one of its recent episodes, “Bones” gave tribute to Sweets, Zack and Vincent, as if honouring the show’s past and setting the seeds for the series finale. At home, Brennan and Booth are now stable again. Booth has recovered from slipping into gambling addiction, and they are now a solid family of four.

“Bones” Season 12 is not expected to shake up Booth and Brennan’s marriage, based on Collier’s teasers. Developments and changes are expected in other couples’ lives. For instance, Camille Saroyan (Tamara Taylor) and Arastoo Vaziri (Pej Vahdat) are getting ready to exchange wedding vows.

For their part, Angela Montenegro (Michaela Conlin) and Jack Hodgins (TJ Thyne) could receive some good news about his paralysis. Daisy Wick (Carla Gallo) joins the team in “Bones” Season 11, Episode 21 (penultimate episode). Daisy gets to deliver the good news to Hodgins that his nerves may be waking up. Hodgins may be able to walk again!

RELATED: ‘Bones’ Season 11, Episode 16 Spoilers: John Boyd’s James Aubrey, Pentatonix in acapella crime [VIDEO]

“Bones” Season 11, Episode 22 is expected to set the stage for “Bones” Season 12. Who is the new villain? Was he in the first season of the Fox series? Fans are expected to find out soon enough.

WATCH: 'Puppet Master' serial killer in 'Bones' Season 11 Finale