On “The Flash,” Grant Gustin’s titular hero isn’t the only character with special abilities, and in the Oct. 21 episode, we’ll meet another DC Comics icon: Robbie Amell’s Ronnie Raymond, aka one half of Firestorm — DC’s “Nuclear Man.” In the series, Ronnie is an engineer on STAR Labs’ particle accelerator, the device that imbues Barry, Ronnie and many other bystanders with unforeseen powers after it malfunctions. He’s also the fiance of Caitlin Snow (Danielle Panabaker), and this week’s episode will flash back (no pun intended) to the night when the accelerator exploded, supposedly killing Ronnie even as it gifted Barry with super speed.

Amell is no stranger to super powers — having headlined Greg Berlanti, Phil Klemmer and Julie Plec’s “Tomorrow People” for The CW last season — and it’s safe to say that heroics are in his genes, given that his cousin is “Arrow” star Stephen Amell. Variety talked with Amell ahead of his “Flash” debut to learn more about Ronnie Raymond’s unfortunate circumstances, his relationship with Caitlin and the logistics of playing a hero whose head bursts into flame. Above, check out an exclusive clip of Amell in action as Ronnie from tonight’s episode, titled “Things You Can’t Outrun.”

Who is Ronnie Raymond — how would you define him when we first meet him?

As a fan of the show, I’ve been reading the scripts and I’ve watched the same amount of episodes as the fans — I’ve only seen one and two — and a really cool thing about my character is, I really see through Danielle’s character, Caitlin, and she’s a completely different person with my character than she is with everyone else. She’s this scientist, a little neurotic, and then Ronnie can break down those walls — he’s got a sense of humor about him. Even though he works in STAR Labs, he’s very much the hammer-and-nails guy, he’s hands-on — it’s like he’s a mechanic working with a bunch of scientists.

What do you think draws him to Caitlin?

We haven’t got to work too much through our relationship yet but the nice thing was, it was on the page one way, and the first thing we shot were scenes between Danielle and I, and they were like, “feel free to improvise and do your own thing, we want it to feel like you guys didn’t just meet today.” And the nice thing was that Danielle and I have a couple of mutual friends and we just chatted on set before we shot anything and she’s so sweet and so great in that character, we just had fun. I’ve seen some clips and it seems like it came across well so hopefully people see some chemistry.

What is Ronnie’s take on Dr. Harrison Wells (Tom Cavanagh) — the audience has already seen a very different side of him than the STAR Labs team has at this point, but does Ronnie have any suspicions?

My guess is… I haven’t done much with him other than the flashback scenes, but I think that Dr. Wells has him fooled just like everybody else. He’s a smart guy, he knows what he’s doing. As an audience member, I love when a character has something hidden from everyone except the audience and he’s such a phenomenal actor that it’s a blast to watch him. It’ll be tough for future scenes not to play that I know anything.

How will the particle accelerator have changed Ronnie mentally, as well as physically, when we next see him?

When you find my character in an upcoming episode, which will be airing in December, one of the cool things is, you meet Ronnie Raymond in episode three, but in December you get to meet Firestorm. I’m a big fan of the comics and DC sent me a big package with action figures and stuff, and when they find my character he’s in a very, very weird state of mind; he’s confused, he’s not really sure what’s going on. You don’t know if I’m a good guy or a bad guy when you first find me, so I think it’s going to be pretty awesome. It’ll be a huge episode, and I may not be the only Amell in that episode…

What can you preview about Ronnie’s dynamic with Martin Stein, the other half of Firestorm, played by Victor Garber?

The unreal Victor Garber… Victor and I actually worked together on a TV movie two years ago (“The Hunters”), and we had such a blast. My fiancee is the biggest “Titanic” fan in the world and when she found out I was shooting with Victor Garber — we shot in Vancouver — and she’s like, “I’m coming to Vancouver.” She came to visit and he couldn’t have been nicer. He spotted her before I did, I was on set when she arrived — he realized who she was, I had mentioned how much she loved the movie and how big a fan she was, because she also loved “Alias,” and he was like, “I’m off soon, you don’t want to stay here and hang out watching Robbie — why don’t you come back to the [hotel] and we can hang out and I can tell you about the movie?” They had a great time, they had some wine and they just had a blast together, and I just really liked him after that moment, because we hadn’t spent much time together yet. We ended up shooting for about a month together. Getting to play opposite somebody that talented and that funny and that creative, hopefully it turns out to be a good dynamic.

Ronnie has been described as “impulsive,” whereas Martin sounds a little more mature…

Yeah. [Laughs.] Part of the character of Ronnie is that I think he’s a little goofy. I think that’s how he levels out someone like Caitlin — he doesn’t take things too seriously. That’s definitely not the way he is when they find him in December, but there’s a little bit of goofiness with him before everything goes down and I’m sure it’ll come back to him shortly. Playing opposite Martin Stein, who’s this genius and a little bit of an older, more mature, by-the-book sort of guy, it should be good.

Can you give us any hints about what might happen if Martin and Ronnie don’t manage to separate themselves? From the way it’s being teased, that seems like it might be a very bad thing…

Yeah, I need to start working on my Victor Garber impression. [Laughs.] There’s definitely a fight for control inside of Firestorm and sometimes it’s Ronnie who comes out and sometimes it’s Martin Stein. So when we aren’t separated, it’s physically me playing Firestorm, but sometimes it’s Martin Stein inside my head… things are gonna get weird.

What’s the process like physically when you’re shooting? There must be a lot of green screen and visual effects work.

In the episode that airs [tonight], in a lot of the scenes we had some green screen background so I didn’t even know what it was going to look like, and Greg Berlanti showed me a couple of scenes when I went by to say hi to the writers’ room and it really looked great. They do such a good job on that show with everything, but the visual effects are really second to none. Armen [Kevorkian], who is the VFX supervisor, took me to [have] a full body and face scan done, and the amount of detail they can use is unbelievable — it was the same place they took Grant to make the digital doubles of him when he’s running at hyperspeed. I’m pretty pumped to see myself as Firestorm, I think it’s going to be pretty badass. But it’s not nearly as cool when I’m shooting as Firestorm: they’re like, “Okay, and now his head’s on fire, and his hands are on fire, and he’s shooting nuclear energy!” And I’m like, “Damn, this is not nearly as cool as I hope it’s gonna look.”

You have some experience playing a character with powers thanks to “The Tomorrow People,” so how does “The Flash” differ from that?

What’s amazing is there’s about 70 percent of the same crew on “The Flash” as there was on “The Tomorrow People,” it felt like I was coming back for a second season, almost. It’s just nice to work with a lot of the same people, people who really cared about our show and had a great time making it, and they were asking me about other cast members… it was really nice to come back to such a good group of people. I think even though the characters aren’t too similar, the way he shoots nuclear energy out of his hands is kind of like a TK blast. There’s definitely a tiny bit of Stephen Jameson in Ronnie Raymond, but it’s more physically than anything else.

“The Flash” airs Tuesdays at 8 p.m. on The CW.