Credit: Patrick McElhenney/FOX

Bones returns to Monday nights next week with the final stretch of its ninth season, which promises to present Booth and Brennan with a situation like none they’ve ever experienced, according to executive producer Stephen Nathan.

“Sort of the past few years, the cliffhanger was Pelant [Andrew Leeds]. It was a serial killer. This time, we wanted our ongoing threat — at least from the end of season 9 to the beginning of season 10 — to be something very vague and conspiratorial rather than one evil person,” he tells EW. “It took us in a very, very different direction and put the characters in situations we haven’t seen before.”

For details, check out our chat with Nathan, where he talks about Cam’s (Tamara Taylor) first meeting with Arastoo’s (Pej Vahdat) parents, Wendell’s (Michael Grant Terry) cancer struggles, and whether or not Booth (David Boreanaz) and Bones (Emily Deschanel) will be planning for baby No. 2 any time soon. Also, check out an exclusive clip from Monday’s episode!

ENTERTAINMENT WEEKLY: First things first: Are you happy to be back on Mondays?

STEPHEN NATHAN: We are. The reality is that Friday worked out very well for us. And we brought the amazing Bones audience over to Friday nights when they hadn’t had that big of a night in a long, long time. So we were very gratified to see how loyal and committed those fans are. But we’re really happy to be back on Monday night. It was a great night for us. There’s a lot of competition, but fortunately people have other ways of viewing the show as well. We’re very happy to be back.

In this first episode back, Freddie Prinze Jr. returns as Booth’s buddy Danny. They have some pretty interesting struggles in this one as friends.

This one was great. We were glad we got one that was a little meatier…and it was kind of an important episode to do for us, and it was nice to see this friendship between Booth and Danny go through so much conflict and see how it ended. And also [we explored] what a relationship really means when it’s with someone who has so many secrets. The murder was meaningful for us just in terms of who the victim was, and what she stood for, and what she meant. It meant a lot to us as well.

Is this the last of Freddie we’ll see this season?

This season, it probably is because we’re planning quite a big upheaval toward the end of the season. In order to earn that, it’s going to take us three or four episodes to lead up to that. So those are carefully constructed episodes, which does leave us with the opportunity to bring Danny back next year — especially toward the beginning of the year. He’s terrific.

Tell me about the upheaval.

We’re leading to another kind of [season] end for the show, something which will turn everything we’ve come to rely on in terms of what’s the solid ground under our feet. That all gets turned upside down, and Booth and Brennan find themselves out in the cold, really — completely alone. Everything they had trusted before is suspect at this point, and it’s sort of a slow-building realization that there is a conspiracy within the FBI that will affect both of them in a way that I don’t really want to give away now, because part of what we see happen to Booth is great — and then things turn.

I heard there will be a few new characters this season. What can you tell me about them?

Those new characters might not necessarily be set up in the finale — they will exist by the finale. We will be peppering in some new people starting in 915, the one that airs March 17, with a new intern who is a defector from Cuba. And we will be seeing some new people appearing. We’re going to meet the deputy director of the FBI. Booth will be in a situation where his fate could change within the FBI very much for the better — which is a cause of conflict between him and Brennan.

Is this conflict because it could change the nature of their working relationship?

It could change the nature of their working relationship, it could change where they work. So it’s a big thing for them to go through as partners and a very big thing for them to go through as a married couple.

What else is going on with our favorites toward the end of the season?

We find out that…Clark [Eugene Byrd] is writing a book, like Brennan. We look at Arastoo and Cam’s life together and meet Arastoo’s parents. And when you bring your parents to meet the woman you love, things always become very complicated. This is certainly one of those times. So we’ll see them. Wendell will come back, still battling his cancer, and we’ll see how he’s doing and whether or not he can continue at the Jeffersonian. That’s an episode that dovetails very nicely with what he’s going through. So we’re able to highlight an issue that’s in the news now, which is we have a murder involving a medical marijuana dispensary and Wendell going through cancer. So we learn a lot of stuff about him through that. And then we will, as promised, contend with the Ghost Killer, which will lead us off on a far more complicated and conspiratorial journey than any of us would have expected dealing with a simple serial killer.

So he is part of the finale?

Yes. This sort of will kick off the finale.

I have to ask you this but I’m sure you get it all the time — are there any plans to expand Booth and Brennan’s family?

You know, they’re busy. While that will be an issue that will be dealt with next year, how they deal with is it is still something we’re trying to discover.

You’ve been renewed for a tenth season. Does it feel like you’re heading into a last act?

No. It very well might be the end of the series, but from where we’re sitting, we’ve heard that before. And even if characters are in the middle of the last act, they never know it. So we have to continue to write these characters as if we’re going to follow them and be with them and grow old with them, to be perfectly honest. So we have to keep this series going. If we find out that season 10 is in fact the end, then we will move toward a conclusion that’s been in the back of our minds for some seasons. But we will construct it with the knowledge that it will end or continue because I think it would be a fool’s bet to say that season 10 is definitely the end.

Here’s a clip from Monday’s episode: