Warning: Spoilers ahead for "Westworld" season three, episode two, "The Winter Line."

Luke Hemsworth stars as Ashley Stubbs in "Westworld," and for most of the first two seasons his character was portrayed as human.

But as the season two finale (and Sunday's episode) revealed, Stubbs is actually a host.

Insider spoke with Hemsworth about this reveal, plus his fight scene, "Jurassic Park," and the tricky concept of free will.

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The "Westworld" season two finale contained many confounding revelations, but the most mysterious of these might have been when the head of security, Ashley Stubbs (played by Luke Hemsworth), seemingly outed himself as a host.

The episode's director, Fred Toye, confirmed this robot revelation to Vanity Fair's Joanna Robinson on the "Still Watching: Westworld" podcast. Now, "Westworld" season three has made the reveal even more explicit with a scene between Stubbs and Bernard in Sunday's episode, "The Winter Line."

"There'd been hints along the way," Hemsworth said in an interview with Insider ahead of the season three premiere.

Hemsworth says he'd guessed that Stubbs was a host, but co-creator Jonathan Nolan would dodge his questions about the possibility. He didn't know for certain until last-minute script rewrites were emailed to him the night before shooting the season two finale scene on the beach (when Stubbs seemingly outs himself as a host while speaking with Dolores).

Insider spoke with Hemsworth about this stressful revelation, what it's like finally getting to act like a host, and much more.

Keep reading for our full interview.

Bernard and Stubbs in the pilot episode of "Westworld." HBO

Kim Renfro: The first thing I wanted to talk to you about was the big reveal last season. When did you learn that Stubbs was a host?

Luke Hemsworth: There'd been hints along the way. I kept hassling Jonah every time I saw him [laughing]. To the point where he would go, "Look, that's your one question" and turn and walk away and I was like "Ah, wait, wait! OK...."

Renfro: Like you would say, "Am I—"

Hemsworth: I would say "Hey, I just want to talk to you about —" [and Jonah would say] "Yep. That's your one question."

Renfro: So you didn't know for sure one way or another?

Hemsworth: I didn't know for sure, but I think the nature of the show is that everyone suspects, I guess. And it's the question of "Who are we? Where do we come from? Where are we going?"

But actually that day I was on the other side of the country and my flight had been delayed and, it was a huge day on set — that day on the beach. There were hundreds of extras. I had a 5 a.m. call [time], and because the flight got pushed I wasn't gonna get there until about 11 a.m.

So I was really, really stressed and I was awake that night, and then they sent through another whole page of rewrites. Which I wouldn't've seen if I hadn't been awake, so it was kind of fortuitous. There were a lot of reveals in what they sent me that night.

Stubbs in the season two finale beach scene. HBO

Hemsworth [continued]: My mind was just like... if I couldn't sleep before then I definitely couldn't sleep after that. I was like, "Holy! What!" Then we got there and Fred [Toye] was directing that one. He was really frazzled as well.

We just took our time and man, somehow we're able to just get it. It was a really nice scene, and Fred came up afterward and he said, "Thanks so much." He hugged me and he was like, "All the chaos and everything and that was just this beautiful little moment between you guys." It was really nice.

Renfro: So then you were finally able to talk Jonah about it.

Hemsworth: [laughing] Yeah it's become easier. He still limits my questions, because I like to badger him a lot.

Renfro: What were some of the other questions that you still had?

Hemsworth: There were always still questions about, for me, who exactly does Stubbs work for? And I think that's addressed in this season a little better. But up until that point, it was always like, "What? Who? Where? Who am I reporting to, and what is Delos? And, but hold on a second, if I'm created here, then, what?"

Renfro: In this episode, it's very heavily inferred that Ford was the one who made him—

Hemsworth: Yes.

Renfro: And it was specifically to protect the hosts and then more specifically to protect Bernard once Bernard seemed to be like getting to the danger zone of.

Hemsworth: Right. It's interesting to play with this idea that Stubbs actually was aware that he was a host the whole time, which I don't think anyone else has that to wrap their heads around. But it's good. I think it crystallized his decisions a little better for me.

Luke Hemsworth as Stubbs in "Westworld" season one. HBO

Renfro: There's that interesting point that Stubbs makes, which is like, "I didn't get some like sob backstory." Is there part of you that thinks it would have been easier to have one?

Hemsworth: Again, it's complete faith in our creators, and so who am I to think that, "Hey we should have had all this information at day one?" They have a master plan and I can't fault them for why they've unfolded that with everybody. It's ego and it's part of the preparation to try and ... you always want to know as much information as you can and if you don't have that information, then your brain stops to make up little stories anyway [laughing]. So yes, Stubbs like fishing and, you know, beer.

Stubbs' fight scene was changed after Hemsworth 'snapped his bicep' while hanging up a TV

Renfro: Let's talk about your fight scenes.

Hemsworth: The funny thing is, the first big fight that I had when we're leaving the park with the guys in the hallway, I actually snapped my bicep off the bone two days before that. So when [Stubbs] gets shot in the arm, that was something we had to do because I couldn't move my arm properly.

Renfro: Oh my God. How did that happen?

Hemsworth: I was hanging a TV by myself on a ladder and just — it was a big TV. It was really big. And it was a really long way up. I was just kind of bouncing it to get it onto the brackets and it just went like [makes a popping sound]. It was like an ax chop. But I got the TV on! [laughing] Somehow the TV was on the brackets and it's still there to this day.

Renfro: So they wrote in there—

Hemsworth: They had to write it in because physically I could barely lift my arm and then I had surgery the following week. That whole fight scene is one-handed because, uh, yeah.

Season three, episode two, "The Winter Line." HBO

One of Hemsworth's scenes from Sunday's 'Westworld' helped reveal a new park and a 'Game of Thrones' cameo

Renfro: Were you excited to see — I've been calling it "Medieval World" to myself, but now I think it's more of a "Fantasy World" because of the "Game of Thrones" tie-in?

Hemsworth: What … which world is this?

Renfro: So that fight scene you were just talking about when you're in the Delos facilities.

Hemsworth: Oh yes, yes, yes, yes. But I still haven't [seen the episode]. I mean, I saw it then. But I feel like — is there a dragon in that scene as well?

Renfro: Yeah, it's literally Drogon from "Game of Thrones."

Hemsworth: That's awesome. Fantastic. Because I was staring at a silver ball.

Renfro: So you didn't know?

Hemsworth: I can't remember whether Jonah told us it was going to be that ... I think he did actually, now that I'm recalling.

Season three, episode two, "The Winter Line." HBO

Renfro: Like Medieval or Fantasy World?

Hemsworth: Yeah. I'm recalling something about the dragon now, but yeah, I can't wait to see it. I love "Game of Thrones" and I love this idea of a crossover. We should just borrow their actors [laughing].

Renfro: For Westeros World!

Hemsworth: Westeros world, yeah! I always wanted a "Jurassic Park" world. I always figured we were selling ourselves short by not going there.

Renfro: There's still one park now that we don't know what it is. We're down, we know five now. So maybe they're saving—

Hemsworth: [laughing] I just gave away something, sorry. Jurassic World. We're going to find the big fella.

Hemsworth isn't convinced the hosts can truly have 'free will'

Renfro: The tagline for this season — freewill is not free — is very intriguing to me and especially for all of the actors who are playing hosts. I'm wondering how you feel like that links up with Stubb's experience this season.

Hemsworth: I think, again, Stubbs is a strange anomaly. And the fact that he tried to discontinue himself, said a lot about going towards free will and having the free will to do that. Unfortunately, he doesn't do it very well.

Renfro: Right, which is interesting because he's ... a robot.

Hemsworth: It is very interesting. Yeah. He's just not a very good shot, I think—

Renfro: But he is in virtually every other scenario.

Hemsworth: Right, right. Yeah. And it's interesting that that's the catalyst to pull him back into a life that is predetermined by someone else. Or is governed by someone else.

Renfro: Like he tried to take himself out of having that be an option, and failed.

Hemsworth: Yeah. Yes, yes. Hmm. It's interesting. But maybe that's the point. The point is the illusion of free will. That's what we're all dealing with.

Jeffrey Wright plays Bernard in "Westworld." John P. Johnson/HBO

Renfro: And immediately after that he has that very pointed line to Bernard, which is like, "If your free will wound up bringing you straight back here, then maybe this isn't what it's cracked up to be."

Hemsworth: Yup. Yup. Yup. Yup. I don't know how to answer that question other than, "yes." I think free will is possibly an illusion. Or ... I mean definitely for the hosts, it is. And I think we're finding that out about the people in the real world, right? That there's a predetermined algorithm which is controlling things.

Renfro: Right. And like this idea that if it's like a self-fulfilling prophecy thing where if you predict that someone's going to do something, simply the fact of observing that.

Hemsworth: It's quantum physics!

Renfro: Yeah. It's hard to wrap your brain sometimes.

Renfro: What was the question? [laughing].

Renfro: Trust me, my brain turns into mush about every episode.

Hemsworth: I definitely read each episode a couple of times.

Why getting to act like a host in 'diagnostic mode' was so exciting

Luke Hemsworth and Evan Rachel Wood in the pilot episode of "Westworld." HBO

Renfro: It's interesting hearing you say that you had wondered, or you were privately theorizing that Stubbs might be a host, but this season we now know for sure. So you got to fully enter "host mode." What was that like?

Hemsworth: It's cool. It's really cool. And it's an evolutionary process in terms of finding out exactly how bodies move when they're in, "diagnostic mode "or whatever it is. And then what happens in those shifts. That's all the good stuff, it's so fun to turn that stuff on and off.

I've been watching the best do it right from the start. One of my first scenes was with Evan when I'm questioning her in diagnostic mode. And so watching her do that was like just mesmerizing. And then seeing Jeffrey do it, and Thandie. I think I've seen everyone do it at some point. So it's good. Yeah. Hopefully, I was doing it right [laughing].

Renfro: The dialogue choices were so smart because it sounds for a second- like Stubbs is just saying like, "What the f---?" or "f--- you" or something.

Hemsworth: It's just barely disguised contempt. I love Stubbs' "f--- you," actually. I think he uses that to great effect. There's a couple of good ones coming [laughing]. Spoiler alert!

This interview has been edited and condensed for clarity.

"Westworld" season three continues next Sunday at 9 p.m. ET on HBO.