[WARNING: The following story contains spoilers about Sunday's episode of Quantico. Read at your own risk.]

Shelby just has to have the Haases.

A week after sleeping with Caleb (Graham Rogers) on Quantico, we learned on Sunday's episode that Shelby (Johanna Braddy) has been hooking up with his father Clayton (Mark Pellegrino) in the present, with Grand Central, natch, as their meet-up spot. "I haven't seen the episode yet and I'm nervous," Braddy tells TVGuide.com. "I'm nervous people are going to hate Shelby. I mean, how do you justify sleeping with your boyfriend's dad?" See what else Braddy has to say about the familial twist, who she thinks is the bomber and what's next.

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You shouldn't sleep with your boyfriend's father.
Johanna Braddy:
I know! It's pretty hard to justify. It's a difficult one. ... [There's] a lot of relationship drama coming up. Since that can of worms has been opened, there's a lot of stuff with her and Caleb in the future. Their relationship has now completely changed once that information scratches the surface. At Quantico, you'll see their relationship develop and you'll walk through it with them, so it's the complete opposite trajectory.

Do you know what happened between her and Caleb that they were no longer on speaking terms after Quantico?
Braddy:
I know a little bit what happens to her between the timelines. She hardens up a bit. She's just sort of shut off.

Her explanation to Alex (Priyanka Chopra) was that she and Clayton just happened and she didn't seem that contrite about it, just embarrassed that Alex found out.
Braddy:
I think she genuinely thought she cared for Clayton. The thing she's drawn to in Clayton is what she's drawn to in Caleb. I think she really cares for both of them. It's just that Clayton has a maturity that Caleb doesn't. Caleb is quite young - he's five years younger than her - and a lot more immature than Shelby is. So she sees a quality she likes of Caleb in Clayton, so she started to fall for him.

Does Clayton feel the same way or is he just desperate to get out of his marriage?
Braddy:
I think they're both pretty logical people and they wanted to explore it because it is something that they're truly feeling. Shelby's not an evil person. She wouldn't sleep with someone's dad out of revenge and I don't think his father would cheat on his wife and get with a young student if he didn't really have feelings too.

But he knows she dated his son, doesn't he?
Braddy:
Yeah, he knows that she did. But you know what? Sometimes you can't help who you fall for. I try not to judge. It is pretty crazy, but I'm not gonna judge Shelby in this situation because who knows where we're all gonna end up.

This doesn't exonerate Shelby or Clayton for the bombing since they were staying right by Grand Central and her previous alibi was Buenos Aires.
Braddy:
Oh yeah. I think it can totally be Shelby. I keep telling the writers that I think it's Shelby. I have no idea if it is, but that's who I have my finger on at this point. There are so many reasons - the ties to 9/11 and stuff I've learned about the character. I just feel like there are a lot of reasons she could've done it. Maybe she thought 9/11 was a conspiracy theory, so she's going against the American government. I don't know, but I have these justifications in my head. You have to because none of us knows who it is and you have to play your character as if you could be the terrorist. ... Now we know she was right there. I feel like a lot of signs are pointing to Shelby.

If she is guilty, do you think that's why she's helping Alex, just to keep an eye on her and throw her off her track?
Braddy:
I guess so. I guess if she were guilty, that's what she'd be doing. But there's also the other half of the character I have to play where she's completely innocent and she believes Alex is innocent too. Alex is her best friend. They went through some stuff that you guys will find out a few episodes from now, but obviously they're extremely close friends.

Alex told her a few weeks ago, "Your whole world fell to pieces when I found out the truth about your parents." Do you know what that is? Did her parents not die in 9/11?
Braddy:
That's a fun one! Let's throw out some options! ... I do know what that is. We had to have a whole secret side meeting about that because I didn't know how to play a scene, so I had a conversation with the writers and I'm pretty sure I'm the only one who knows what that line means, so I'm definitely not saying!

What about her half-sister? Is she real? Is Shelby actually wiring all that money to her?
Braddy:
That's what's going on right now, yes. ... I know some information about [her sister] that you'll learn very soon.

Does she actually like Caleb?
Braddy:
Their feelings for each other are genuine. I think it's that "love to hate them and then you love them"-type thing. He was annoying her at first, but I think she came around the more she was around him. That's how it started. The closer they got, the more she got to see other sides to him as well. There's good to him as well, so she actually fell for him. You'll see it's not just a fling.

And then she falls for his father.
Braddy: Yeah, she just really wants the Haas family. It's something about those men! Haas squared!

There was almost a throwaway line where Shelby mentions that Caleb's mom is in office. Will we see who she is?
Braddy:
I don't specifically know what [she is]. She's a politician of sorts. We haven't really delved into his mother yet.

Do you or Shelby know who Mark Raymond is?
Braddy:
Not at this point she doesn't. ... I dunno who he could be. I kinda want to be surprised by it. I don't want to make too many decisions. Doing that, I could be completely wrong about him, so I kinda want to take each episode fresh with an open mind. Maybe Shelby found out about Mark Raymond and that's why [she and Caleb don't speak].

Quantico airs Sundays at 10/9c on ABC.