Nestor Carbonell and Sarah Michelle Gellar

Nestor Carbonell went from protecting an island on Lost to doing the same thing for Sarah Michelle Gellar's runaway twin on Ringer.

"She is my island, that's for sure," Carbonell tells TVGuide.com of Agent Machado's obsessive need to track down Bridget in order to protect her from a vicious killer he's trying to take down.

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Unfortunately for Machado, Bridget has taken on the identity of her presumed-dead twin sister Siobhan and she's not going to give up her secret anytime soon. Carbonell discusses Machado's motivations, the emotional side of Ringer and whether he'll figure out who "Siobhan" really is:

Do you think Agent Machado has any idea that Siobhan is actually Bridget?
Nestor Carbonell:
I don't think he's made the leap, but he knows something's amiss. I have a feeling he's not far from doing that. But she's quite good; she really is. There's a couple of twists coming up in the next few episodes where you think he really has got her, and she's just managed to evade everybody.  He's not far from sort of cracking that piece of the case.

Why is Bodaway's case so important to him? Is there a deeper connection we'll come to learn?
Carbonell:
I think there's a strong back story that explains why it's so important to me. I have been told that... there's something personal there that's beyond the professional. In fact I'm shooting a scene [now] — we're on Episode 107 — where again, I'm trying every angle to get this guy, so it's clearly something that's personal for him. On the surface, we all have a duplicitous nature so I definitely believe that there's something fishy there.

How far will he take this investigation?
Carbonell:
He's essentially moved to New York. He's not from there, but he's moved here until he cracks the case or until he finds Bridget. We will see him go back to Wyoming at some point, but he's pretty much around New York. 

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What does he think he can get from "Siobhan," really?
Carbonell:
Siobhan, right now, is the last person who allegedly saw Bridget or spoke to Bridget. So that's the best lead he's got right now. You'll find out that he gets a big clue, something that he's been looking for; a piece of hard evidence that really implicates Siobhan in some way. He will eventually come up with something that he's been looking for and he thinks he's got her, and we'll see if he does.

Might "Siobhan" be using him in return?
Carbonell:
Absolutely. I really feel like she's very smart. She knows how to work around the law; she's done it before and she's now hiding in plain sight in her sister's identity. She's using everything she can to piece together her own sister's life and again, with respect to me, she absolutely uses me to find out information about Bodaway or Malcolm [Mike Colter].

How is she going to continue to keep this secret?
Carbonell: As each episode progresses you'll see that stories slow down considerably and you'll see her sort of navigate through her new identity. The writers really sustained the story to the point where we're like, "Oh no. We're buying it. We're with you. We're with Bridget on the ride."  We'll see where it takes us. But so far, I don't feel that it's been stretched thin at all.

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Where is the season heading?
Carbonell:
Really, at the heart of it is Bridget's dynamic with Andrew [Ioan Gruffudd], which is one of the most interesting things and the most compelling things. Is she, oddly enough, going to save this marriage? As a viewer, you're probably rooting for her to do that in an odd way. That becomes perhaps one of the bigger emotional components. Her relationship with Juliet [Zoey Duetch] is important. Malcolm will come into the mix as well; he's an old true love of hers. It just becomes more personal and emotional.

How does Machado's devotion to Bridget and the Bodaway case compare to Alpert's devotion to the island?
Carbonell:
She is my island, that's for sure. I am chained to that island; I am chained to Bridget.  While the goal really is to put Bodaway behind bars, she is the key to that goal.

Ringer airs Tuesdays 9/8c on The CW.