David Boreanaz, Emily Deschanel David Boreanaz, Emily Deschanel

Bones begins its eighth season with lots of unanswered questions, but there's one in particular that many of the show's characters must ask this season: Is love enough?

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"What we are trying to do this season is have everybody re-examining their relationships," executive producer Stephan Nathan tells TVGuide.com. "[Last season] everyone came together, everybody's relationships were solidified, and it was kind of a happy season. All of that got pulled apart at the end of the year, and now everybody is seeing the world in a new way."

The man behind that fracturing is serial killer Christopher Pelant (Andrew Leeds), who in the Season 7 finale used his hacking skills to frame Dr. Brennan (Emily Deschanel) for murder. Realizing the only way to fight Pelant was to go off the grid, Brennan took Baby Christine and went on the lam with her ex-con father (guest star Ryan O'Neal), leaving Booth (David Boreanaz) behind. On Monday's premiere (8/7c, Fox), a blonde (!) Brennan finally resurfaces, offering clues that will help her pals at the Jeffersonian both solve the murder  of a guidance counselor and perhaps prove her innocence.

But how will Booth react when he comes face-to-face with Brennan again? "When you haven't seen somebody for three months, you're terrified. You don't really know whether they're well, whether they're in danger, or how much danger they're in," Nathan says. "I think the initial reaction is relief and gratitude that [Brennan and Christine] are fine, and also just happiness that you're with this person that you love again."

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Brennan will still have a lot of 'splainin' to do once the happiness of the reunion wears off. "We start to see the effects of this separation and how difficult it has been for Booth," Nathan says of the season's second episode, which involves the murder of a high-profile divorce attorney. "That's where [Booth] realizes he resents this person, that he's angry at her. And Brennan harbors some anger and resentment as well."What's Brennan got to be angry about? "She has lived her entire life independently," Nathan says. "She's realizing for the first time that she's terribly interconnected with Booth... and this kind of shakes the foundation of who she feels she's been all these years. [She may] resent the fact that she gave herself over to another person. These are all very complicated feelings... and Brennan is going to have to confront certain psychological aspects of her own life that she would never before have entertained."But Nathan says that will be true for everyone this season. Sweets (John Francis Daley) will be forced to rethink his relationship with Daisy (guest star Carla Gallo) when he's partnered with a new FBI agent (guest star Danielle Panabaker). Cam (Tamara Taylor) will also pursue a surprising new love interest, while Angela (Michaela Conlin) and Hodgins (TJ Thyne) will have to contend with Angela's discontent.

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"Angela originally entered into her situation at the Jeffersonian on a part-time basis, mostly out of friendship for Brennan," Nathan says. "She was an artist. She had a trajectory for her life that was compromised. So she and Hodgins will be going through a reevaluation of their situation."Hodgins will also be the first person to really let the Pelant case get under his skin. The result is one of the premiere's most shocking moments. Suffice it to say, you've never seen this side of Hodgins. "I think these people are discovering things about themselves, perhaps some dark things, that they wouldn't normally have confronted," Nathan says.  "But they are now dealing with [Pelant], somebody who is besting them at every turn. This causes a lot of friction, a lot of anger."

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While it's hardly a spoiler to suggest that Brennan will be back at the Jeffersonian by the end of the premiere, Nathan promises Pelant's story is far from over. (The killer will likely resurface sometime around January.) But the team — and viewers — will have plenty to scratch their heads about in the meantime."All I can say really is nothing is as it seems," Nathan says. "Pelant is disorienting in every way. He disorients all of our characters, and when they are disoriented, it's a matter of trying to find our footing again. That's a lot of what Season 8 is: trying to find our footing, trying to find out what's true, both emotionally and practically in [the characters'] lives."And could the truth for Booth and Brennan be that love isn't enough? "They are tested," Nathan says. "It's something that will kind of torture them throughout the season. We would like to believe that love is enough for Booth and Brennan, but that doesn't mean it's going to be easy. ... Everybody's life will be altered. Everybody is evolving, and that's never a pain-free process."Bones premieres Monday at 8/7c on Fox.