Y/N got out of the stretcher he had been sitting in for the past few hours and took off the cast on his wrist. Enough of his arm had healed to where he didn't need it anymore. The young man then walked over to the door into the lab Caitlin had gone into. 

Looking through the window into the lab, he saw the brunette sitting on a bench. She was looking down at her hand, fiddling with the engagement ring on her finger. Y/N sighed before opening the door and entering.

Caitlin saw him enter and gently nodded. Y/N indicated if it was fine for him to sit down and she offered the space next to him. For the next few moments, the two just sat in silence before Y/N decided to talk.

Y/N: I'm sorry. I didn't mean to scare you, leaving like that.

Caitlin: It's okay. I get it. You had to go. It's just... That's the last thing that Ronnie said to me that night.

Y/N nodded in understanding. He started to think about his own grief, about how he acted, or rather still acted, in a similar manner anytime his parents were brought up.

Y/N: My parents died fourteen years ago. I used to think that the further away I got from it, the less it would hurt. But some days, the pain, it's worse than the day that it happened. Some things you can't fight.

Caitlin: For so long, I've been terrified of reliving that day. Of reliving the pain and telling people what happened.

Y/N: Why did you tell me?

She turned her head and looked at him, her eyes glossy and holding back tears.

Caitlin: Because you looked like someone who would truly understand. And someone I could trust.

Y/N nodded, putting his head down low. He pulled a tissue out of his pocket and handed it to her. Caitlin gratefully accepted it, wiping the tears from her eyes. After a long silence, Y/N tried to change the subject. He cleared his throat and grabbed a stack of folders.

Y/N: I, uh... went through some of your work. The things you were doing before the accident.

He brought the folders down, placing it between the two of them. Caitlin looked at the large stack beside her.

Caitlin: How did you...

Y/N: Fast reading, remember?

She nodded, looking back down at the notes.

Y/N: I've got to say, it's really good. Brilliant, in fact. This whole thing is phenomenal. I mean, the mere concept of an individualized, hidden persona within the human body that changes not only mental cognition, but biological appearance as well is incredible! To think that different personalities can cause us not just to change our emotional programing but our skin cells as well! It's like you're remixing human tissue into something that's similar yet different.

Caitlin's expression changed. She went from weeping to chuckling at Y/N's clear excitement over her work. The girl's face showed a bright smile.

Caitlin: Thanks. It was a passion project of mine for years. I began testing by exposing skin cells to a temperature lower than -12 degrees Celsius. Over time, the cells started to change on their own depending on the emotion exhibited by the processer I put them under without even needing to experience a drop in temperature.

Y/N: Why didn't you publish it? 

The brunette shrugged.

Caitlin: 'Cause most would have called me crazy. Most people don't really see this type of work as rooted in true science. Even my own mother dismissed it. Dr. Wells was the only one to believe in me. We planned on working on it together after the accelerator was up and running.

Y/N: Well, I think it's spectacular, and that's coming from a fellow scientist. And if and when it inevitably happens, you get to play the "I told you so" card.

He gave her a bright smile. Caitlin giggled, craning her head back a bit. Y/N then noticed her eyes fall back on the engagement ring. Looking over towards the side of the room, he spotted a few vials and beakers full of chemicals. He got an idea.

Y/N: Hang on. Let me show you something.

He got up and walked over to the chemicals, putting on a nearby lab coat and gloves. Caitlin got up and followed him, watching him work in curiosity. He took out a small vial, and poured in a set of chemicals. Using his speed, he quickly spun around the vial, mixing the chemicals.

After a bit, he then lit a small match and dropped it in the vile of chemicals. The small chemicals lit on fire, creating a controlled burn. Reacting within the millisecond, Y/N grabbed a vial of liquid nitrogen and added it to the mix. He then capped the vial and stirred it all together again. After a moment, Y/N was left with his finished mixture.

Y/N: There we go.

Caitlin looked at the vial in shock. The entire content inside was frozen solid. While the fire was not actually burning, there were hints of orange at the center of the frozen batch that resembled flames. It looked like someone had painted the ice inside to look like an orange crystal.

Y/N: It's a little concoction I thought up a little while back. I used your notes to actually finish the process, using my speed to get it to the millisecond I desired. By mixing in sodium, nitrogen, and phosphorus paired with oxygen and a cooling agent, along with my incredibly quick reaction time, I was able to create a frozen reaction. Essentially a fossilized image of a chemical combustion.

Caitlin looked at the ice vial in awe and amazement. Looking proud at his achievement, Y/N then handed out the vial to her.

Y/N: I want you to have it.

Caitlin looked at him questioningly.

Y/N: "Fire and ice". Something to remember Ronnie by, remind you that he's always with you.

The brunette looked at the vial for a moment, stunned. She then carefully took it, examining it and holding it close to her chest. She looked up at Y/N with a happy expression of sorrow.

Caitlin: Thank you.

Y/N simply nodded at her, smiling back. 

Cisco and Wells were just finishing up the bio-dampening devices. They included a set of handcuffs as well as a few small disks that could be placed in a cell once Girder was captured. The two finished and smiled at their project.

Cisco: Yeah, baby!

Wells: Well done, Mr. Ramon.

Wells held out his hand to shake. Cisco thought they were doing a bro handshake and stumbled with his fingers. The two moved their hands awkwardly, unsure what the other was doing. They decided to just stop and leave it at that.

As they finished their project, another news alert came on. The metal man had returned wreaking havoc near a construction zone. Y/N and Caitlin walked into the room, seeing the broadcast.

Cisco: Looks like Optimus Past-his-Prime has returned. 

Y/N looked at the broadcast, deciding to take his time with this one and think through a plan.

Y/N: So, how do we stop him? I'm all for suggestions as long as they don't involve me breaking my hand again.

The others all looked at each other. Cisco and Wells had been thinking this through as well.

Wells: Any material, if struck at a high enough velocity can be compromised.

Cisco: We ran an analysis based on Girder's appearance as well as the damage he inflicted upon you. Based on our hypothesized density and atomic structure, if you impact it at just the right angle, at just the right speed, you could do some serious damage.

Y/N and Caitlin peaked up at that.

Y/N: Great. Now we're talking science. How fast would I have to go?

Cisco: Factoring in the metal's possible tensile strength, estimated dermal thickness, atmospheric pressure, air temp, you'd have to hit approximately... Mach 1.1.

Caitlin: You want Y/N to hit something at 800 mph? 

Cisco: 837, actually.

Caitlin: That's faster than the speed of sound! 

Cisco: I know. You would create a sonic boom, which is awesome.

Caitlin: You've never gone that fast. There's no telling what it could do to your body. 

Y/N: I have to try.

Caitlin: This is insane. You would need a straight shot from miles away.

Wells: Do it right, and you'll beat him.

Y/N: Do we know the exact distance I'll need?

Cisco: I'm still working on that calculation right now.

Caitlin groaned and made her over to Cisco, helping him with the calculations. The group heard screaming coming from the TV. Girder was now tossing around cars and threatening to tear down an entire crane. Caitlin turned to Y/N.

Caitlin: You need to go. We'll finish up the calculations and tell you when we have a number.

Y/N looked at her for a moment. She looked back at him like he had just asked a dumb question.

Caitlin: Go!

Y/N nodded and rushed out, grabbing his suit and the handcuffs in the process. He made his way across town. People in the streets stood in awe at seeing a red flash of light rocket through Central City. 

At the construction site, Girder grabbed onto a large steel beam. He tossed it towards two workers who had fallen on their butts. They screamed but were suddenly saved by a quick blur grabbing them and pulling them to the side.

Y/N ran in, getting everyone out. When he was finished he ran back into the site and stopped, eyeing the metal man in front of him. Girder grinned, flexing his muscles and cracking his knuckles.

Y/N: Hello again, Rock'em Sock'em. 

Girder: So, the flash of light wants more? I'll gladly deliver it to you.

Both men stood their ground, eyeing each other. Girder then rushed towards Y/N. He threw a punch, with it appearing in slow motion to Y/N. The fast man dodged it and ducked under another blow. He jumped up and kicked the man from behind.

Y/N: Too slow, Tin Man. 

Girder threw another punch. Y/N dodged it and ran around behind the metal man, causing Girder to punch and dent a shipping container.

Y/N: Let me guess. You're one of those guys who peaked in high school, right? Never got over it?

Girder growled at Y/N. The fast man grabbed a metal pole and hit it across the brute's face. It merely scraped against his cheek, creating a few sparks as metal hit metal. Girder grabbed the pole with one hand and glared at Y/N.

Y/N: Ah, shit. 

The metal man swung the pole around, throwing Y/N against the dented shipping container. He then turned again, slamming Y/N against a metal beam. The man in red fell down on his chest, hurt. Girder looked down at him.

Girder: So what's your next move, flash?

Y/N looked up at Girder, panting. 

Y/N: Guys, how's it coming?

Cisco: Almost got it...

Caitlin: 5.3 miles! You need to run approximately 5.3 miles.

Y/N glared at Girder. He picked himself up and ran away. Girder watched the fast man run off in a streak of red.

Girder: Pfft. Coward.

Y/N ran to exactly 5.3 miles and stopped. He turned around, getting down on his hands. He had a straight shot back to the construction site. He prepared for take off. Behind his goggles, lightning crackled in his eyes.

Y/N then took off. Above him, a helicopter was showing footage of a red streak running across town. Y/N was moving at high speeds, leaving a trail of lightning behind him.

Cisco: He's gonna do it. Go, man, go!

Y/N continued to run, pushing himself. Glass windows and car screens smashed when he ran past them. Suddenly, as he hit a stop light, a thunderous boom could be heard behind him. He just broke the sound barrier.

Cisco: Yes!

Caitlin looked at the screen in both awe and concern. Dr. Wells smirked and smiled upon seeing Y/N moving at record speeds. The fast flash of red light continued on his journey.

At the construction site, Girder heard the thunderous boom. He turned around to see the red streak approaching him. Then, just as he was mere feet away, Y/N leaped into the air towards the metal man. He brought back his fist before swinging it forward.

Y/N hit Girder right on the cheek, denting the metal and knocking him out. Both men fell to the ground as a ripple of sound blew out around them.

Cisco: Supersonic punch, baby! Whoo!

Caitlin: Y/N? Y/N, are you okay?

Y/N groaned and rolled over on his back. He saw the metal man next to him lying in the dirt unconscious. He pulled himself up.

Y/N: Yeah, I'm okay. 

Y/N walked over to Girder. He pulled out the set of bio-dampening cuffs and placed them on Girder's arms. Almost immediately, the metal man's skin turned back to a normal, tan color.

Y/N: It's over.

Later, Dt. West and other CCPD officers pulled up to the scene. They walked through the construction sight with their guns raised. Some held flashlights to try and find their culprit.

The lights soon fell on an unconscious man sitting on the ground. He was sitting with his back against the wall, his hands restrained by a pair of cuffs. On his chest was a hand written note along with a bag of some strange devices. The note read, "One tin man who needs a heart. Do not remove cuffs. Place devices inside cell to null effects. Keep on at all times. -- Flash of Light"

Joe looked at the note and exhaled. A slight smirk appeared on the corner of his lip.