Bones Bones

The Ghost Killer may be dead on Bones, but she will continue to haunt Booth and Brennan during the Season 9 finale (Monday at 8/7c, Fox).

As Booth (David Boreanaz) prepares to be confirmed for his new role at the FBI during a congressional hearing, he receives a phone call from a conspiracy blogger who claims to have information linking the Ghost Killer's family —the McNamaras — to some FBI brass. Unfortunately, the blogger ends up dead before Booth and Brennan (Emily Deschanel) get a chance to connect the dots.

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"Brennan thinks she's done with the Ghost Killer, but in an indirect way, she's not," Deschanel tells "When you get a phone call from a mysterious person talking about a conspiracy and they end up dead, it's very suspicious." Adds executive producerStephen Nathan: "They uncover what appears to be a conspiracy that is far, far larger than the Ghost Killer. What we wanted to do, because we have been dealing with serial killers on a relatively regular basis on the show, was take this in another direction and make this rabbit hole that they're falling down far more nefarious and conspiratorial than we have ever seen before."

As Brennan investigates the blogger's cause of death, Booth digs deeper into the McNamara-FBI connection. But for obvious reasons, Booth must keep his work quiet. "He certainly is suspicious about the FBI and other government agencies," Deschanel says. "We start uncovering some pretty intense stuff. We have to keep it under wraps because we don't know who to trust at the FBI — or anywhere really."

And Booth's investigation into his own agency will take an emotional toll on him. "Booth is a guy who is incredibly honest, incredibly just and uncompromising, and I don't think he'll ever change," Nathan says. "But what we're doing is putting him up against a situation which is the opposite." Adds Deschanel: "Booth believes in his country and he believes in the FBI. He sees these as a few individuals who have abused their power. That doesn't shake his confidence in the bureau or his government ... but that doesn't mean he isn't willing to take those people down in whatever way possible. It becomes a hunt for these people, and Booth has to fight them."

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Indeed, that intense firefight becomes the centerpiece of what is arguably the biggest, most action-packed finale the show has ever done. And Boreanaz was not only dodging bullets but he was also the man calling the shots behind the camera. "It's always a challenge to take on something like the season finale," Boreanaz says. "With this specific finale, there was so much information that we had to gather up and put out there in one 45-minute hit, it made it difficult and challenging. Whether it was dealing with the big huge hearing with Congress or an intense battle between other forces that could come in and jeopardize Bones and Booth's relationship...  it definitely was draining. By the end of it, you're pretty exhausted."

And viewers may find themselves exhausted by the end as well. As these grim promos tease, Booth will be fighting for his life. "It all comes to a head, and it's pretty detrimental," Boreanaz says. "It puts them in a different place." Adds Deschanel: "I wouldn't categorize this as a happy ending. It changes everything. Booth always has faith that the good guy wins, but in this situation, it doesn't look good."

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But Booth's survival isn't even the biggest question of the finale. In fact, it's the season's closing seconds that will have the most impact on what the show will look like in Season 10. 

"Everything — Booth's work, Booth's relationship [with Brennan], and the direction of Booth and Brennan's life — will be called into question at the end of this season," Nathan says. "People will be changed by what has happened at the end of Season 9 and what will occur at the top of Season 10. The show as we all know it will continue; it will just continue in a different way."

Bones' Season 9 finale airs Monday at 8/7c on Fox. For more on the finale, check out our Watch This Tonight video below. Plus: Catch up on past episodes of Bones here.