Caitlin, Barry, and Wells stand in Caitlin's lab while Professor Stein lay, sedated, in the med bed. Barry is looking at Caitlin, trying to gauge her reaction to finding out Ronnie is alive. She hasn't taken her eyes off the monitors.

"Cait?" Barry says softly.

She grunts, eyes fixed, unfocused, on the monitors.

"Barry, will you give us a moment?" Wells asks.

Barry nods and exits the lab.

"Caity?" Wells says, wheeling closing to her. Her grabs her arm and lightly pulls her away from the monitor. She turns and focuses on Wells. He can see the confusion and fear in her eyes.

"He's alive," she whispers to him, looking at Ronnie's body out of the corner of her eye.

Wells sighs and turns to look at Ronnie.

"Do you remember when you were younger and you'd get so mad at me for bringing my work home?"

A small smile breaks on her face and she nods.

"You used to say work didn't belong at home." He chuckled to himself a little, remembering 14-year-old Caitlin sitting with her arms crossed, begging him to take a break. "Do you remember what I would tell you?"

"I am a scientist, and a scientist's work is never finished." She said.

"A scientist's work is never finished," he repeats in a whisper.

A few moments of silence pass.

"My work did this to him. To both of them. And my work won't be finished until I bring them both home." He says, now looking at Caitlin.

She turns to look at him, an unsure look on her face. He squeezes her hand and takes a deep breath. "I promise."

Caitlin nods and looks to Professor Stein over on the bed. She crosses her arms and huffs. "What do you think? Keep him sedated?" She asks.

"We could. Do you think you could give him something to calm him down? Make him more lucid?" Wells asks.

"I'm sure I could figure something out."

"Then do that. Keep him sedated until then." Wells says, wheeling out of her lab. She sits down at her desk, looking back at the monitors, focusing this time.

*****************************************

"Do you think we can separate them?" Barry asks. Him, Caitlin, and Wells are sitting in the cortex. Caitlin is spinning in her chair, staring up at the ceiling. Barry is witting on a desk, tapping his hand nervously against the top of it.

Wells, who is sitting behind the control panel, looks over his glasses at Barry. "Is it possible? Theoretically." He says, nodding his head side to side. "But splitting an atom and splitting a man are two very different things."

Barry nods, returning to his tapping. They have been waiting for about half an hour. Caitlin gave Stein some meds to help clear him up and then stopped the drop of the sedative that was keeping him asleep. She asked Barry to pick up some clothes for him and a razor. She laid the clothes, razor, and scissors out on the table next to the bed. Now they were just waiting.

Stein walks into the cortex. Barry sees him first and hops off the table. Wells turns to look at him. Caitlin notices Barry's reaction and turns in the chair to see what he's looking at. What she sees makes her stomach drop. She stands up slowly, not taking her eyes off the man that looks exactly like her fiance that, up until a few hours ago, she thought was dead.

"I don't suppose it's necessary to point out you're all staring." Stein says, an annoyed looked on his face.

"Our apologies." Wells says, looking at Caitlin.

Stein walks further into the room. "I feel clearer than I have since the accident. What did you give me?" He asks, looking at Caitlin who he assumes gave him the drugs.

"A cocktail of anti-psychotics, depressants, and mood stabilizers." Wells answers, causing Stein to turn and look at him.

"The same formula used to treat dissociative identity disorder." Stein observes. He turns to looks back at Caitlin. "I assume this was your idea. Very clever, Cait."

Caitlin flinches at the nickname, and though she doesn't see it, Barry winces at it too.

"Uh, don't call me that. Please" She responds, a weak smile on her face. "We'd like to run some tests on you if you don't mind."

"Of course, Dr. Snow." Stein answers, nodding to her.

Stein walks back into her lab. Caitlin doesn't immediately follow. She stands there looking at him. Barry walks up and puts his hand on her back. "Are you okay?"

"I'm just...confused." She answers.

"Do you want me to go with you?" Barry asks.

Caitlin turns and looks up at him. She nods. "Please."

They walk into the lab and see Stein already sitting on the bed. Caitlin takes a deep breath and looks at Barry. He nods, and she begins, putting on her best doctor voice, hoping not to crack.

After running all the physical tests, she sits down across from Stein. "Are you comfortable?"

"A little warm, but overall feeling fine." He answers.

"What do you remember? About the night you changed." She asks.

"Everything. From my point of view, at least. I can't say the same for Mr. Raymond." Stein answers.

"You said you could feel him." Caitlin says, looking down in her lap. "Is he"

"Still alive? Yes. Just...dormant, I believe would be the word." Stein responds. "His presence becomes stronger at times. Usually when you are around. Which is why, I'm assuming, we were unable to maintain control of the matrix."

She looks up at him.

"Do you feel in control of the matrix now?" Barry asks. He is standing behind Caitlin, leaning against her desk.

"Yes. As I said...I feel clear." Stein responds. "I don't feel him as much."

"The drugs. You're in control of your thoughts right now." Caitlin explains.

"It's not the thoughts that have troubled me. It's the memories that aren't mine." Stein answers. "Some are stronger than others. One has been very strong since the beginning." His face softens and he looks directly at Caitlin. "The Hudson Falls at Piedmont State Park. I've never been, but I remember those waterfalls perfectly."

Caitlin stands up and walks back to her desk next to Barry. He looks down at her, worried.

She turns to see Dr. Wells knocking on the glass window that connects to another lab. He motions for her and Barry to come in.

"We'll be right back." Barry says as him and Caitlin head into the other lab.

"Dr. Snow!" Stein calls.

Caitlin turns to look at him.

"What was the memory?" He asks.

Caitlin looks down. "It was...That's where he proposed to me."

Stein smiles. "He loves you very much. That I can feel"

Wells is glaring at the computer screen when they enter the other lab.

"This doesn't make sense. Why is it all Ronnie's body, but both of their minds?" Caitlin says to Barry.

He scoffs. "This whole thing is confusing."

"What isn't confusing, is what's happening to him now." Wells says, not looking away from the screen. "Ronnie's body is rejecting Stein's atoms like a host rejecting a parasite."

Caitlin and Barry walk over to look at the screen.

"If his temperature continues to rise..." Caitlin starts.

"What?" Barry asks.

Wells turns to look at both of them. "He could go nuclear."

Cisco walks into the cortex and notices no one is there. He walks into Caitlin's lab and freezes at the sight of Stein.

"Ronnie?" He says, taking a few quick steps toward Stein.

Stein shakes his head.

"Professor Stein." Cisco says, pointing at him.

Stein points into the other lab. "Your friends are in there, not so subtly talking about my condition."

Cisco walks into the lab, points to them, then Stein, then himself, and then he stares at his finger and puts it down. "What happened?"

"You'd know if you'd been here. Where the hell have you been?" Caitlin asks, curiously.

"I was helping Joe on a case." Cisco says, almost convincingly.Caitlin furrows her eyebrows at him.

Wells catches Cisco up on Ronnie's condition.

"How long does he have?" Cisco asks.

"Based on the current rate of increase..." Wells says, looking at Caitlin. She looks back at him...pissed.

Wells' face softens. "A couple of hours."

Cisco grabs hair at the top of his head. "You can separate them before that though right?" He says, panicked.

"Any attempt to separate them could result in a catastrophic nuclear explosion. One that would level the entire city." Wells explains.

Cisco and Barry both sigh and look down. Caitlin clenches her jaw.

"Unless the host body was no longer functional." Wells says, not making eye contact with any of them.

"You wanna...the host body...Ronnie...you wanna kill Ronnie?" Cisco exclaims.

Wells winces at hearing it, but stiffens back up. "It's two lives...for millions." He argues.

Cisco starts to argue back but Caitlin cuts him off.

"Can you give us a minute." She says sternly, not taking her eyes off Wells.

Barry and Cisco walk back into Caitlin's lab, leaving Wells and Caitlin in the connecting room.

Wells sighs, "Caity, I"

"No." She says taking a step toward him. "I can't Wells. You cannot ask me to do this again. I can't lose him again."

"I don't know what else to do." Wells admits.

"You promised me. You promised you'd bring him home. I know what I've said to you but...he's back. He's...he's there. Right there. I have a chance. I'm not losing it." She says. "You said you have two hours." She leans over just enough to make close eye contact with Wells. "Use them."

Caitlin walks out of the lab. A few moments later, Cisco walks back in.

"You wouldn't really kill Ronnie, would you?" Cisco asks, paranoid.

"Stay here, Cisco." Wells orders, wheeling out of the lab.

Barry is sitting in Caitlin's lab with Stein. They have exchanged a few awkward glances and half-smiles.

"I remember you, Mr. Allen." Stein says, breaking the silence. "You were on the train. that day, on the way to the particle accelerator launch. You were going to meet a girl, but not your girlfriend." Stein says, imitating the same stuttering Barry had when he first told him.

"Yeah," he chuckles. "That turned out to be the least of my worries that night."

"I take it things didn't go well with said not girlfriend?" Stein asks.

"That's not the one I'm concerned about," Barry says, half-smiling.

"You know, Einstein was a bit of a romantic himself." Stein says, recalling their conversation on the train. "He once said, 'any man who can drive safely while with a pretty girl is simply not giving the girl the attention she deserves.'"

Barry smiles, and looks over to the cortex where Caitlin recently walked out. Stein's eyes follow Barry's and he looks back at Barry, raising an eyebrow.

"Can I get you anything?" Barry asks, breaking his attention away from the cortex. "It might be a while before they're done."

"A bottle of Chateau Petrus 1982 would be nice." Stein smiles. "Or maybe not. These taste buds might be very different from my own. Maybe now I'm a light beer guy."

"There are worse things to be." Barry says, chuckling.

Stein walks around the panel to face Barry. "Like a living nuclear bomb?"

Barry turns to Stein with wide eyes. "How did you"

"Unstable nuclear fission was always a danger in the transmutation process." Stein says. "Plus, you all argue very loudly."

Barry looks apologetically at Stein. "We're gonna find a way to fix it."

Stein nods and walks out of the cortex.

Wells wheels back into the lab where Cisco is still sitting. "I need your help," he says, holding a box of tools in his lap.

Cisco nods and moves to help him.

Caitlin comes back into the lab, sitting at her desk and watching the numbers on the screen rise, as the clock in the corner ticks down.

Wells and Cisco enter the room. "We got it!" Cisco announces.

Wells wheels in behind him. "It's a bit of a Hail Mary but we're gonna give it a shot."

"I'll go get him." Barry says, running out of the room. He returns, alone. "He's gone."

"Cisco, find him!" Wells yells, wheeling over to the screen.

"The tracker says he's thirty miles out of town." Cisco announces.

"Minimum safe distance." Wells says, not to anyone in particular.

"How long do we have?" Caitlin asks.

"Twelve minutes. Are you almost done, Cisco?"

"Done," he says, handing the device to Wells to finish programming it. "This is a splicer. Put it on Stein and it should separate him from Ronnie. Once you get it on him, run." Cisco instructs.

"Even you can't outrun a nuclear blast." Wells says, finishing up the device and handing it up to Barry.

Caitlin grabs it out of Wells' hand before Barry can and walks out of the room. She starts putting on her jacket.

"What are you doing?" Barry asks.

"I'm going with you."

"No you're not." Wells says loudly from the other room.

"Cait, it's too dangerous." Barry says, walking toward her.

"There's not enough time for Cisco to talk you through how to work the splicer and there definitely isn't enough time for arguing." She says, staring at Barry. "Let's go."

Barry and Caitlin lock eyes for only a second before he picks her up and runs out.

They stop in the middle of nowhere, thirty miles outside of Central City. They look around and see Stein standing a few yards away, holding a gun to his head.

"Professor Stein!" Caitlin yells, running to him. "Professor Stein, please wait!"

"Get her out of here!" Stein yells at Barry.

Caitlin gets closer to him. "Please, Ronnie is still in there."

"I won't let all those people die, Cait." Stein says.

"We can separate you." Barry yells from behind Caitlin.

"How?" Stein asks.

"Shut up and let me do this." Caitlin says, activating the splicer.

Caitlin takes a step forward while working with the device. From where he's standing, Barry can see Stein's facial features soften, staring at Caitlin.

"You're sure this will work?" Stein asks, as quietly as he can while still being heard.

"No. But I'm not losing him again." Caitlin says, finishing up on the splicer.

She looks up at him, meeting his eyes. He reaches his hand out to her and pulls her head to his, kissing her harshly. She keeps her hands around the splicer but leans into him. He pulls away and looks at her with a sad smile.

"That was from him." Stein whispers to her.

Caitlin takes a step back and smiles at him. "I look forward to meeting you in person, Professor." She attaches the splicer to his chest and presses a button in the center. She takes another step back. Barry runs up beside her as they watch.

Stein starts yelling as his body lights on fire.

"It's not working," Caitlin says just loud enough for Barry to hear her.

"Cait we gotta go." Barry says.

"No..." She looks on at Stein as he loses more control of the matrix.

"Get her out of there!" Wells yells through Barry's comms.

Barry grabs Caitlin and she clings to him, not taking her eyes off Stein. Off Ronnie. They start to run away and she watches as the barren land in front of her goes up in smoke and dirt. They're knocked forward and Barry tries reaching for Caitlin as they roll.

....

"Barry!" Wells yells through the comms.

"Cait..." Barry looks down at Caitlin who is pressed against him, eyes closed.

"Cait!"

"Is she okay?" Wells yells.

"...ow..." she groans as she opens her eyes. "Well that plan blew up in our faces didn't it."

Barry hears Cisco snort over the comms and Wells sighs.

"It back fired a little yeah" Barry says, smiling at her.

Caitlin doesn't make eye contact and immediately looks to the center of the already clearing explosion. "Ronnie..." Caitlin whispers.

"There's no radiation being detected from Barry's suit." Cisco says.

"It wasn't nuclear?" Caitlin asks, looking up at Barry.

He runs her back to where they left Stein and where there was now a large crater in the land.

Barry and Caitlin make their way down into the crater, covering their mouths, trying not the breathe in the smoke. Ronnie's body appears amidst the clearing smoke. Caitlin runs up and kneels down next to him. He coughs and looks up at her.

"Tell me your name." She says.

"Ronnie Raymond," he says smiling at her. She lowers her head to his chest and wraps her arms over him. He lays his head back on the ground and sighs, smiling.

"Obviously I need a change of clothes." Stein, now in his own body, says as he walks toward the other three.

"Nice to see you in the flesh again, Professor." Barry says. He smiles at Caitlin and Ronnie.

"What happened?" Cisco asks through the comms. "Did it work?"

"Yeah," Barry says. "We're coming home." 

A/N:

Hey everyone, so fair warning, there is going to be some Ronnie and Caitlin plot in the next few chapters, but it all goes toward developing Caitlin and Barry's relationship. I said this would be multiple books long, so there is plenty of time for Snowbarry. But their friendship is an important part of their relationship and her and Ronnie is something that needs worked out as much as Barry and Iris, which, again, will come into play later. 

Peace and Love! -Ali