Barry was almost glad when trivia night was cut short by a report of Leonard Snart robbing the Central City Museum. Despite his best intentions to the contrary, Iris' continued insistence that he ask Felicity out had pretty much ruined any chance he'd had of having fun. He had absolutely no desire to get in the middle of whatever the hell it was that was going on between Felicity and Oliver, but he didn't bother trying to explain that to Iris because he didn't know how. By the time Eddie had gotten the text about the sighting of Snart, Barry had been starting to look for an out, for absolutely anything that would give him an excuse to leave.

"I'll cover for you," Felicity told him, following him out the door.

"All right, what are you going to say?" Barry asked.

"I usually tell people that Oliver is at a nightclub, with a girl, or nursing a hangover," Felicity replied.

"None of which will work for me," Barry pointed out, though in the back of his mind, he was wondering, And people believe that? Apparently, Oliver worked a lot harder at maintaining his playboy persona for the sake of protecting his secret identity than he'd thought.

"Oh!" Felicity exclaimed as a solution apparently came to her suddenly. "I tell them something happened with your sister."

"What kind of something?" Barry asked warily. "Because I don't want Iris to worry-"

"Just go!" Felicity interjected, making a shooing gesture. Barry went. On his to STAR Labs to put on his suit, he called Kara on her cell phone, since he assumed that she wouldn't have a comm on her while she was working her day to day job.

"I need you," he said when she picked up. "Leonard Snart is robbing the Central City Museum. Meet me there as soon as you can." He waited to hear her confirmation of the plan before hanging up and continuing on his way.

Barry arrived at the museum moments later and immediately skidded on a patch of ice on the road outside. He recovered his footing and frowned, wondering how in the hell there was ice on the street in the middle of the evening on a warm day. He didn't have time to think about it too much, though, because a moment later there was a rumbling sound like a sonic boom, and Kara came in for a hard, neat landing beside him. Together, they searched for Snart, and immediately spotted him running into the theater across the street from the museum, Joe hot on his heels. Barry and Kara quickly followed after them, running inside the building in time to see Snart fire something that looked like a tongue of white flame from the strange looking weapon in his hand, sending it straight toward Joe. Barry threw himself in front of him, and the white flame struck him in the chest. In an instant, he felt freezing cold, like he'd been outside in the middle of winter for hours without any cold weather gear. His built up momentum made it impossible for him to stop himself or change his trajectory, and he slammed against a column before crashing to the ground.

"Are you okay?" Joe asked, rushing to his side.

"Aggghh," Barry groaned in reply. "It burns."

"Time for a test run!" Snart shouted, filling Barry with dread. Whatever he meant by that, it couldn't be anything good. "Let's see just how good the two of you are!" Out of the corner of his eye, Barry saw Joe cast a puzzled look in his direction, which confused him until he remembered that he didn't know about Kara- or, more specifically, he didn't know that Kara had joined him in his superhero crusade. He didn't know that two people had stopped the armed car robbery earlier, but Snart obviously did. Barry watched in horror as he fired his strange weapon at nearby innocent bystanders, one by one, then felt relief as each time as a red and blue blur that he knew to be Kara moved Snart's unfortunate targets out of the way just in time.

The battle between Snart and Kara moved into an open theater nearby. Barry forced himself to his feet, moving as fast as he could manage while still feeling the effects of Snart's weapon. He entered the theater in time to see Kara shove an usher out of the way of a beam from Snart's weapon only to be struck by it herself just as Barry had been not long before.

"No!" Barry screamed, rushing to his sister's side as she fell to the floor. In the periphery of his vision, he saw Snart slip out of an emergency exit, but right now the only thing he cared about was Kara.

"Are you okay?" he asked.

"Yeah," Kara said in a strained voice, struggling upright. There was a thin coating of ice over the emblem on her chest. "I'm fine. Invulnerable, remember?" A pause, then she added, "But it looks like you're not okay." She looked around for Snart, realized he was gone, and went on, "Let's get to STAR Labs so they can fix you up." Barry nodded and helped Kara to her feet, and then they were off.

"It's still numb," he informed Caitlin as she was examining the spot where the strange white flame from Snart's weapon had struck him a short time later.

"It's presenting itself as third degree frostbite," she told him in reply, frowning, though whether in concern or bewilderment, he couldn't tell.

"I thought he had hyper healing," Felicity put in.

"It's been slowed," Caitlin replied. To Barry, she said, "If your cells weren't regenerating at the rate they are, your blood vessels would have frozen solid and the nerve damage would have been permanent. You're lucky to be alive."

"Snar wasn't another metahuman," Barry said. "He had some kind of gun. It froze things. It slowed me down, enough that Kara had to pick up my slack, and she could have been killed because of it."

"According to his records, Snart didn't even bother to finish high school," Felicity spoke up, surprising absolutely no one with the fact that she knew that information off hand, "so how did he manage to build a handheld high tech snow machine?"

"STAR Labs built the cold gun," Doctor Wells admitted in a dry tone of voice.

"Doctor Wells and Caitlin had nothing to do with this," Cisco said suddenly. "I built the gun."

"You did?" Barry asked. "Why?"

"Because speed and cold are opposites," Cisco explained. "Temperature is measured by how quickly the atoms of something are oscillating. The faster they are, the hotter it is, and when things are cold, they're slower on the atomic level. When there's no movement at all, it's called-"

"Absolute zero," Barry cut in.

"Yeah," Cisco confirmed. "I designed a compact cryoengine to achieve absolute zero. I built it to stop you. I didn't know who you were then, Barry. I mean, what if you turned out to be some psycho, like Mardon, or Nimbus?"

"But I didn't, did I?" Barry demanded, furious.

"We built the entire structure you're standing in to do good, and it blew up," Caitlin said, leaping to Cisco's defense. "In the wake of that, you can understand why Cisco would want to be prepared for the worst."

"I can understand that," Barry conceded, though he was still angry. "But what I can't understand is why you didn't tell me what you did. I mean, after all we've been through, I thought you trusted me! I thought we were friends!"

"We are, Barry," Cisco insisted.

"I mean, if you had told me, I could have been prepared!" Barry went on, on a roll now. "But instead, Kara could have died tonight!"

"And I have to live with that," Cisco said ashamedly.

"No, Cisco," Barry corrected. "We all do." Shaking his head, he turned and stormed out of the Cortex, needing to be alone for a while. Eventually, he found his way to the treadmill. He switched it on and started running, needing to work out his anger and his fear and his guilt, needing to forget.

"Barry!" He heard Felicity calling him a long time later. "Barry!" He switched the treadmill off and turned to see her standing by the door.

"What are you doing?" he asked. "You should go back to your hotel. Get some sleep."

"You should too," Felicity replied. "Not go back to my hotel, I meant get some sleep."

"I can't," Barry said, shaking his head. "Every time I close my eyes, I see Kara lying dead on the floor of that theater. I watched my sister get hurt less than a foot away from me, and I couldn't stop it. And even though it didn't kill her, for all we know, next time it could. I have to go faster."

"Barry, it's not your fault," Felicity said, and for a moment Barry wondered how many times she had told Oliver something similar. "And it's not Cisco's either." There was a moment of silence and she came over to sit beside him on the edge of the treadmill.

"I know you're upset," she went on, "but you have to look at this from his point of view."

"No, I get it," Barry replied. "He didn't trust me."

"Barry, when you first met us- me, Oliver, and Dig- we were this well-oiled archery machine, but we didn't start out that way," Felicity said. "And unlike you guys, we weren't thrown together overnight. We came together one at a time." There was a long pause, then she added, "Believe me, it took much more than watching Oliver do the salmon ladder to make me trust him." She smiled, apparently unconsciously, and Barry wondered for the second time what exactly was between them.

"I've seen firsthand what this life can do to people," she said, and here her voice turned somber, reminding Barry that Team Arrow had suffered a devastating loss recently. "It's a lonely path. Don't make it any lonelier than it has to be." By this time, she was standing by the door, and then, a moment later, she was gone. Barry shook his head and, not knowing what else to do, followed her out of the room and back to the Cortex.

Later, as he was examining a map of the city filling one of the screens set up around the room, he heard footsteps behind him, and then he heard Cisco announce, "I figured out a way to track Captain Cold."

"You gotta stop naming these guys," Caitlin remarked. Barry didn't turn around.

"Barry," Wells said. "Listen to him." Reluctantly, Barry turned away from the screen to face the people arranged around the room.

"How?" he asked, irritation lacing his voice.

"The cold gun is powered by an engine control unit," Cisco explained. "A microcomputer that regulates air to fuel ratios so the subcooled fluid in the chambers doesn't overflow and-"

"Explode," Felicity put in.

"Right," Cisco confirmed, turning to point in her direction. "This ECU was receiving updates wirelessly from my tablet. If I boost the signal using Central City's network and send a false update, we'll get a ping back."

"And then we'll be able to locate Snart," Wells surmised.

"How long will it take?" Barry asked.

"First I have to hack into the city's network," Cisco said. "So I don't know, thirty minutes, maybe?"

"I can do it in less than one," Felicity said, running over to sit down in front of one of the computers in the Cortex. "When it comes to hacking, I'm the fastest woman alive." She tried to crack her knuckles, winced, and exclaimed "Ow! That was not as badass as I pictured." After a few seconds of frenzied typing, she said, "Alright, I'm in."

"Are you kidding?" Caitlin asked, sounding astonished. Barry was unfazed. He knew there was a reason Oliver had Felicity on his team, and that that reason had nothing to do with whatever emotional connection existed between them.

"Alright," Cisco said in an excited tone of voice. "I'm sending the updates. We're connected."

"Network is transmitting the location," Felicity said.

"We got him," Caitlin added after a moment. "He's heading west on Nelson toward the train station."

"If he's leaving, it appears Mr. Snart may have gotten what he came for," Wells said. In an instant, Barry had his suit on, ready to go after Snart.

"When we put our minds to it, dude, nothing can stop us," Cisco said excitedly. Clenching his jaw, Barry found himself locking eyes with Kara as he angrily switched off his comm.

"Oh," Cisco said in a troubled tone. "You turned your earpiece off. How are we supposed to talk to each other?"

"I don't feel like talking right now," Barry replied irritably.

"At least let me go with you," Kara offered.

"No," Barry said. "I want to do this alone." Then, like a shot, he was off. Before he'd really had time to think about what he was doing, before he'd time to come up with a strategy, he was at the train station, and then he was racing alongside the train he'd seen Snart slip onto. In an instant, he crashed through the window and landed inside the train car, crouched in the aisle directly in front of Snart.

"There's nowhere to run!" he cried.

"You know, I didn't see you before?" Snart replied, seemingly unconcerned. "Does your mom know you're out past your bedtime? And where's your red and blue clad friend?"

"If you wanted to get away, you should have taken something faster than a train," Barry said instead of answering his questions.

"That's if I wanted to get away," Snart replied. "I've seen your weakness, at the armored car, then at the theater. See, while you're busy saving everybody, I'll be saving myself." With that, he pointed his gun at the floor of the train and fired. A thin patch of ice spread along the floor, and the train shuddered and groaned as, outside, the wheels froze and an ice formation forced it off the track.

"Good luck with that!" Snart shouted from the door, before leaping out of it and disappearing into the night. Barry hesitated, torn. Snart had to be stopped, but the train was derailing, tipping off of the track, one car at a time, and he had to get all these people out.

Suddenly, with a jolt, the sideways tilting motion of the train stopped. Barry ran to the broken window that he'd entered the train through and looked out it to see Kara, her hands braced against the side of the train, struggling to keep it upright long enough for the passengers to evacuate.

"I've got this!" she shouted in a strained voice. "You go get Snart!" Barry nodded and race off.

Moments later, he found himself facing off against Snart once more. Before he could react, Snart fired his gun at him, the ice cold beam from it knocking him down and pinning him to the ground beneath an ice formation. When Kara appeared a few minutes later, flying out of the darkness of the night toward Snart like a red and blue missile, he did the same to her.

"Pretty good, you two," he said. "But not good enough." A pause, then he added, "Thank you."

"For what?" Barry snarled.

"You forced me to up my game," Snart replied. "Not only with this gun but with how I think about the job. It's been educational." He lifted his cold gun to aim at Barry and Kara, and Barry braced himself for the end.

"Drop it!" Cisco's voice shouted suddenly. Past Snart's shoulder, Barry saw him, Caitlin, and Felicity, carrying a large object glowing with blue-white light between them.

"This is a prototype cold gun," Cisco said when Snart turned his head to look at the three of them. "Four times the size, four times the power."

"I was wondering who you were talking to," Snart remarked to Barry and Kara.

"Hey!" Cisco shouted to draw his attention back toward him. "Unless you want a taste of your own medicine, I'd back the hell up."

"Your hands are shaking," Snart told him. "You've never killed anyone."

"There's a first time for everything, Captain Cold," Cisco replied. "I will shoot you." A long, tense silence followed.

"Alright, you win," Snart finally said, putting his hands up in a gesture of surrender. "I'll see you around." With that, he stepped past them and started to walk away, off into the night.

"Hey!" Cisco called after him. "Leave the diamond."

"Don't push your luck," he said, pausing for just a moment before continuing on his way.

"I couldn't shoot him if I wanted to," Cisco said when Snart had gone. "This is the STAR Labs vacuum cleaner." With a laugh, he added, "With a lot of LEDs."

"Let's get you warm," Felicity said in a soft, concerned voice, crouching at Barry's side and resting a hand on his shoulder.

"Don't worry, I've got it," Kara said, and proceeded to defrost first herself and then Barry with her heat vision.

"And before any of you ask," she said when the group turned to stare at her, "no, I don't know why I didn't think of doing that sooner." They all laughed.

"Thank you," Barry said fervently, looking each of them in the eyes in turn, hoping they would see the silent apology in the gesture. They all nodded, and, as a group, they made their way back to STAR Labs.

Later, after weeks of dealing with the metahuman threats that seemed to crop up all the time these days, like mushrooms after a rain, Barry finally managed to find a few quiet moments to himself to reflect on what had gone down with Leonard Snart. He had no idea what his next move might be, and the team's attempts to track him had come up unfortunately rather short. But one thing was certain- he had, however inadvertently, taught Barry a valuable lesson about trusting his team.