The two halves of Bones' two-hour midseason finale really couldn't be more different.

The first episode (8/7c, Fox) finds Booth (David Boreanaz) and Brennan (Emily Deschanel) dusting off their personas Buck and Wanda to go undercover at an Old West-themed shooting competition to solve a murder.

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"Booth is much more into the idea of going undercover than Brennan is," executive producer Michael Peterson tells TVGuide.com. "She's like, 'This is a waste of time. You just want to wear a silly cowboy hat and guns.' She doesn't believe that it's actually necessary for the case, so she doesn't join him initially. She comes in later, but it changes the dynamic. Every other time they're basically a couple going undercover, and this time they're getting to play strangers to one another. They've been married for so long and to get to see each other in a different dynamic was a fun opportunity we wanted to take."

While Buck and Wanda's relationship is a bit strained, Cam (Tamara Taylor) will take things to another level with photojournalist Sebastian Kohl (Gil Darnell). But don't give up hope on Cam and Arastoo (Pej Vahdat) just yet. "In [Cam's] mind, she's said the words she's not with Arastoo anymore, but I don't think she quite believes it yet. It's not real," Peterson says. "She still loves him dearly, and she has to come to grips with it. She's trying to do what she thinks everybody else wants her to do. She's trying to go on and have a relationship, but I think her heart still belongs to Arastoo."

Get your laughs in early, because the fun stops in the second episode when the team investigates a cop killer. Even worse, the killer plants a bomb in the body of his victim in order to take other cops who come to the crime scene to investigate. Needless to say, not everyone comes out the blast unscathed, including Aubrey (John Boyd). So just how ominous is it?

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"This is the episode that changes everything," Peterson teases. "It's the fulcrum point of our season, and everything will change. It's a pivotal episode. At one point, it was going to be our season opener. It originally was our way of getting Booth and Brennan back into the story, what happens to Aubrey early on."

With Aubrey potentially sidelined, Booth will get some help from behavioral analyst Leslie Green (guest star Sara Rue). And even though she will appear in more episodes later this season, she and Booth get off to a bit of a rocky start. "She's going to bump heads with Booth quite a bit," Peterson says. "She's a bit scatterbrained in her personal life, but she's very good at what she does. She plays a pivotal role, not only in this case, but in Episode 13, we're going to be introducing our new serial killer. She is going to be instrumental in that one."

Meanwhile, Angela (Michaela Conlin) and Hodgins (TJ Thyne) go back and forth about potentially having more children. And although the couple reaches a definitive conclusion, an unforeseen complication will dramatically alter that conversation going forward. And even though Cam fortunately escapes injury at the crime scene, a bomb will go off in her personal life when Arastoo returns to the Jeffersonian unexpectedly.

"The second this bomb goes off and Cam could be in danger. He's there in a flash," Peterson says, which only further establishes the differences between the men in Cam's life at the moment. "Arastoo knows Cam so intimately, he can watch the news and know that Cam would have been involved. Meanwhile, Sebastian doesn't even equate that she's in danger quite as quickly. That's proof of how much closer one relationship is than the other."

Bones' two-hour midseason finale airs Thursday at 8/7c on Fox.