'The Flash' postmortem: Scoop on the fiery final scene

Warning: This story contains major spoilers from Tuesday's episode of The Flash, the first hour in a two-night crossover with Arrow.

Ronnie Raymond has returned and he's looking hot. No, seriously. Hot.

In the closing moments of Tuesday's episode of The Flash, Caitlin's (Danielle Panabaker) assumed dead fiancé Ronnie (Robbie Amell) reappeared engulfed in flames after having been turned into DC Comics superhero Firestorm—though he may not be a hero just yet.

"He's definitely not the same guy he was," Amell tells EW. "He's definitely a dangerous guy. He's a bit of a scary dude at this point. He's more a homeless schizophrenic than Ronnie Raymond."

If it looks like Ronnie has gone a little crazy, that's likely because he's not alone. During the particle accelerator explosion—at least if we're going by comic lore—Ronnie was fused with Dr. Stein (Victor Garber, who will first appear in the 12th episode), a brilliant but arrogant nuclear physicist who makes up the other half of the Firestorm entity. Until Ronnie deduces what's really going on, there's only one person who can stop him. No, not The Flash.

"Caitlin's the only thing that seems to bring a little bit of Ronnie back out of this odd character, but he needs to battle his own demons before he's ready to be the man he was when he left," Amell says.

Suffice it to say, Caitlin and Ronnie's reunion in next week's episode won't be quite what Caitlin imagined. "It's going to be explosive," executive producer Andrew Kreisberg teases. "I wrote this scene where she's saying, 'I used to play this game with myself: What would I give for one more minute with Ronnie?' It's actually a game I played with myself. What would I be willing to give up to get one more minute with somebody I lost? I thought about that Caitlin actually gets her minute, but she wishes she hadn't because of what he becomes now. She actually wishes he just died. Not that she ever had closure, she certainly didn't having lost him, but now it's worse for her because he's walking around and he's not himself. Whether or not he can be brought home becomes part of the second half of the season."

Because it's nearly been a year since the particle accelerator incident, Caitlin has been through a long process of grieving. With the help of Cisco (Carlos Valdes), Barry (Grant Gustin) and Wells (Tom Cavanagh), she has even started to move on. "Helping The Flash, she's got a new focus and purpose in her life," Panabaker says. "She's letting go of the grief and the sadness of Ronnie's death. To be faced with that again all of a sudden is terrifying."

"At first she thinks she's crazy," Panabaker continues. "If you thought you saw your dead fiancé just hanging out at the mall, you might go get your head checked, too. Her initial reaction is disbelief. In the same way she's gone through a lot in the last year, so has he. His is a little bit more violent than what she experienced, so it's surprising and difficult for her. She struggles with why didn't you come back sooner and who are you now? How has this past year changed us?"

Cisco, however, may have a very different reaction. "I definitely think he feels some relief, but at the same time he's grappling with a sense of guilt because he was directly responsible for locking him in a particle accelerator and he feels personally responsible for killing him," Valdes says. "Not only does he have to come to terms with that himself, but he also has to grapple with telling Caitlin and finding a resolve with her."

So, how will The Flash handle this seemingly new foe? "Ronnie's going to remain a secret between Cisco and Caitlin for a hot second until they can find out more about it and figure out if and how they can help Ronnie," Gustin says. "We just shot some stuff where, in the future, they will be dealing with it. Ronnie will be an important part of episode 9, as far as Barry's concerned, in getting him out of trouble, actually, at a certain point. But that's not to say that's going to be a pattern the next time we see Ronnie. He's all over the place and not himself."

"You might see a little bit of a fight between Flash and Ronnie," Amell adds. "You might see Ronnie helping people. He's just a total freak at this point."

Could Ronnie end up being sent to the pipeline prison? "That's always a possibility, but I think if that happened, they would have to deal with the repercussions of their knowledge of Ronnie and their familiarity of Ronnie as a human being," Valdes says. "He was Caitlin's fiancé. He was one of my best friends working in the lab. That's a huge emotional obstacle for both of them."

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