The Bones team has met a new serial killer who's already giving them nightmares.

Thursday's episode featured a corpse that the Smithsonian team discovered was the victim of a serial killer who tortures his victims for weeks and then strings them up like marionette puppets. Worse, the team realizes that the body they've discovered isn't the only victim, and they'll need much more evidence before they can find the culprit.

<em>David Boreanaz and Emily Deschanel</em>David Boreanaz and Emily Deschanel

The last time the team had to hunt a serial killer--Christopher Pelant (Andrew Leeds)--he terrorized them for three seasons, tormenting Booth (David Boreanaz) for years and killing one of their own. As terrifying as Pelant may have been, this new shadowy figure will give the team a different kind of chill, says executive producer Michael Peterson.

"Pelant started off as a hacktivist character and was smarter than [a lot] of people combined. This will be a little more terrifying of a character," he says. "Pelant, as crazy as he was, had a logic to him. This is going into a darker territory than we have traditionally handled on Bones. It's less of a thriller and more of a horror element to it than there was with Pelant. It's going to represent a different kind of danger."

The new killer has a fascination with mother figures, which will spell bad news for a member of the team although Peterson isn't ready to acknowledge who. "It's going to have a profound effect. It is different than other [cases]. It really is going to psychologically mess with a lot of the characters," Peterson says. "The next episode where he is featured is called 'The Nightmare Within the Nightmare.' This is a person that can really haunt your subconscious."

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"The Nightmare within the Nightmare" is slated as the Bones season finale on July 21, but Peterson says that they have plans for this new killer to continue into the series' farewell season too. "We'll probably look at them one more time in this season and one more time next season," he says. "If we're having fun we might go a little longer, but you can expect one more this season and one more [in Season 12]."

What do you think of the new killer on Bones?