'The Flash' star Robbie Amell on Firestorm mythos and a Killer Frost nod

The Flash is about to face off with Firestorm, but this time it’s for a good reason.

After Firestorm—an amalgamation of Ronnie Raymond (Robbie Amell) and Dr. Martin Stein (Victor Garber)—attacks a physicist during Tuesday’s episode of The Flash, Team Flash will set out to track him down in hopes of figuring out exactly what happened to him after the particle accelerator explosion.

Though separating Ronnie and Stein may seem like the obvious conclusion, everyone will come to discover that it’s not so easy, especially once General Eiling (Clancy Brown) returns and sets his sights on Firestorm. Can Ronnie and Stein actually be separated? And will Caitlin’s (Danielle Panabaker) comic book destiny to become Firestorm foe Killer Frost get in the way of her future with Ronnie? EW caught up with Amell to get the scoop:

Does Ronnie realize he is fused with Dr. Stein at this point?

ROBBIE AMELL: The cool thing about this episode is you get to see what happened. It picks up in flashbacks a month after the explosion, so you see what’s been going on with this guy and what’s been building to the last time you saw him. It’s almost an origin story in that way. The only time you’ve really seen Ronnie as Ronnie is in flashbacks in episode 4. The nice thing is that it looks like it’s hopefully building towards figuring out what’s wrong with him and fixing it, but that’s when things get a little dangerous and messed up. Some of the Firestorm lore comes into play with The Splicer and whether or not they can split Stein and Ronnie.

How desperate are they to actually get split?

AMELL: At first, they don’t want to split because they don’t want anybody near them. They’re worried that they’re too dangerous and they don’t want to hurt anybody around them. You’ve got two guys fighting for control of one body and the problem is if one of them isn’t in control, neither of them are, so that’s why you get these lash-out situations, even with the people they love. That definitely continues with this episode.

How will S.T.A.R. Labs help them with this?

AMELL: It doesn’t go very smoothly. You get to see a pretty badass fight scene—an accidental fight scene, if you will. One of the coolest things about it is that only two people on this show have fully digital doubles and those two people are The Flash and Firestorm. You get to see one of the most impressive visual effects/live action fight scenes on the show so far.

What are Ronnie and Stein going through once they are separated? Do they realize they are actually better together?

AMELL: When they separate, Ronnie wants to give it a try with Caitlin again, that’s who he’s been trying to get home to, and it’s the same for Stein and his wife. They go their separate ways. They’ve had more than enough of each other over the past year, but they quickly realize that they aren’t as separated as they think. They’re definitely still connected in a certain way. Like you said, maybe they are better off fused. The only problem is, if they fuse together, can they separate again? A lot of the danger comes into fusing together and separating, and the problems that arise while doing that.

Can you talk about how they’ll go up against General Eiling?

AMELL: That’s part of the reason they need to fuse. They become humans again and they try and do anything they can in that state, but when you’re going up against a big bad like Eiling, who is also coming after you for your superpowers, sometimes it’s better to be a metahuman than a human.

Ronnie wanted Cisco (Carlos Valdes) to lock him in the particle accelerator if he wasn’t back in time, but do you think he harbors any resentment?

AMELL: No, definitely not. One of the nice things is that’s squashed right away. The second that they see each other and Ronnie is in at least somewhat of a clear mental state, Cisco tries to apologize for it and he stops him right away. “No, I told you to do that. You did the right thing. Everybody would’ve died if you didn’t.” There’s no resentment there. They’re good buddies and they’re happy to see each other again.

What does his relationship with Caitlin look like now? Does he hope for some normalcy?

AMELL: Absolutely, but it’s tough. She’s been living this unbelievable life for the last year hunting and taking down metahumans. Ronnie is looking for something a little quieter. He’s gone through this horrible year of not knowing who he was and not knowing if he would ever be himself again. The two of them want to be back to normal, but they’ve both been living these completely different lives for the last year, and things are weird when they get back together.

There seems to be some chemistry between Barry (Grant Gustin) and Caitlin. Does Ronnie pick up on that?

AMELL: Nope, not yet. He’s been homeless and schizophrenic for a year. He’s not picking up on anything.

I’m sure we’re a long way away from Caitlin becoming Killer Frost, but in the comics, Firestorm eventually goes up against her. Will we get any hint towards that at all?

AMELL: In an upcoming episode, you get a very small taste of the future of Killer Frost. But like you said, it’s definitely a ways down the road. I know that Danielle is super excited about it. I know they’ve been talking to her about it. I think it’s a matter of time. I’m sure they’ll start to manifest it shortly, but you have to see the development there, otherwise you’ll feel like you’ve missed a step.

The Flash airs Tuesdays at 8 p.m. ET on The CW.