A/N: Review response - Review 1. (Mischief Managed-Up To No Good) I'm really glad you like the story! It makes my day to hear what everyone thinks of it.

We're starting to really get into it now, with everyone starting to interact. So exciting! I hope you enjoy the third chapter of Running With a S.H.I.E.L.D. at Your Back!

Caitlin saw Cisco and Fitz leave the next morning. She'd gone to her room straight away after dinner the night before, though Barry and Cisco had asked if she wanted to watch a movie. She'd wanted one of two things, and a movie wasn't on her list.

Unfortunately, the thing she wanted most didn't work out. It hadn't worked out in a few weeks, which made each failed attempt weigh more heavily on her. He didn't answer by the end of the second call, which meant he was busy working. So she sent him a message, saying she missed his voice and loved him, and hoped to hear from him soon.

The other thing she wanted was time alone, to think and reflect. She didn't know why she was being so cold to the S.H.I.E.L.D. agents. She realized they seemed like very likable, personable people, nothing like the agents she'd imagined in her head when news of HYDRA had been fresh. Just the fact that they called it S.H.I.E.L.D. meant they probably weren't HYDRA, since that organization had no reason to hide anymore. She chalked up her withdrawnness to the adjustment period. She'd never liked change much. In a few days she would be used to the way these people ran things and, more importantly, know the people better. Then she would let herself warm up to them.

She didn't want to bond with them too quickly, in case they were ripped away.

Try as she might to remain distant, she did have to fight a rush of amusement when Fitz and Simmons said goodbye to each other in the morning. The awkwardness between them was both adorable and painful as they held each other tightly, as if going to get supplies were a dangerous mission. It made her wonder if they knew they cared about each other. It was obvious to her, even from knowing them less than a day, but she knew from experience that being in the situation made it much harder to realize.

Caitlin waved at Cisco and Fitz as they walked towards a plane, where Mack and May were already waiting. Once the loading dock closed behind them Caitlin looked at Barry, and then Simmons. "So what's this field assessment?" she asked.

"A test to see how well you can control your abilities. The first one is meant to be difficult, because you're still getting used to them, but it gives us a point of reference when we start training you. Daisy will be joining us later for part of it."

"How are we doing it?" Barry asked.

Simmons walked into the lab and held up a speedometer and a stopwatch. "The first part is simple. For the most part, we'll do it the old-fashioned way, to determine your top speed and reaction times. After, I'd like to do a biological analysis. Dr. Snow, I thought you'd like to help me there."

"Absolutely," Caitlin said.

"Great," Simmons said with a little bounce. "After that Daisy will take over. If you're ready, Barry, we'll go to the training site now."

"I thought you didn't have one yet?" Barry asked.

"We don't; Coulson cleared a space for you to practice in while Fitz and Cisco work on a more adequate one."

"Must be a small space if he cleared it out in one night," Barry said as they walked. Caitlin didn't say anything, and was only half surprised when they reached their destination. "Or not," Barry said. The room was about half the size of a football field, surrounded by thick gray walls. The floor was a smoothed cement, and there seemed to be imprints in several locations.

"What did you keep here?" Caitlin asked.

Simmons closed the door behind them. "S.H.I.E.L.D. used to be much larger. You didn't think we only had one plane, did you?"

"Nice," Barry said, still looking around. Caitlin followed his gaze up and saw that the slightly domed roof was retractable. That explained how the planes got out so quickly.

Simmons went to stand midway across the room, staying to the right side. "Whenever you're ready, Barry, just run around the room."

"Just once?"

"For the moment, yes."

So began a series of tests. Caitlin watched and recorded the speeds as Simmons called them out. Simmons made Barry do a single lap, then multiple variations of laps, some to determine speed alone and others to record reaction time combined with speed. They were there for well over an hour before Simmons said she had enough for the first part of the field assessment. Barry stumbled to a stop and leaned heavily against the wall, his face glistening with sweat.

Caitlin walked up to him, mentally assessing his condition. "You need to eat," she said, noticing how weak he seemed. He hadn't passed out since the first few days, but this was the longest period of straight running he'd done.

Simmons came over and took the clipboard with the measurements from Caitlin. "I've got just the thing in the lab. I'm terribly sorry if I pushed you too hard," she said fretfully.

"You didn't," Barry said, straightening. "I would have told you. But Caitlin's right that I need food."

They walked back to the lab, and Caitlin noticed that Simmons kept looking at Barry as much as she did. Caitlin stood next to Barry and made sure he ate the three high protein bars Simmons gave him. Apparently the S.H.I.E.L.D. scientist kept supplies in a variety of locations throughout the base, in case she was ever trapped in one. You never know when you might need even the most basic supplies, she had said as she handed the bars and a jug of water over. Caitlin noticed the tension in her shoulders, the way she adjusted her stance, and realized something must have happened to her. In the recent past, if she had to hazard a guess. Simmons didn't say anything to explain, and Caitlin left it alone.

"These aren't bad," Barry said between bites and gulps of water. "They're no Big Belly Burger, but nothing is."

The tension in Simmons' shoulders eased. Apparently that comment was sufficient distraction from whatever she had gone through.

They relaxed for a few minutes to give Barry's stomach time to settle, and then Simmons looked at Caitlin with a glimmer of excitement. "This is the part I like best: the science."

Caitlin turned to Barry while Simmons grabbed medical supplies. He sighed. "Shirt off?"

"Yep."

He took off the long-sleeved blue shirt as Simmons came over with gel and medical pads. "I'd like to measure the electricity in your system," she said as she turned. When she saw Barry, she faltered for a second, and Caitlin almost smiled. She'd done physicals for colleagues before, and understood perfectly the initial biological reaction to a fit body. Barry was definitely fit. Just as quickly as Simmons faltered she recovered herself, and handed Caitlin half of the pads. "This won't hurt, and will record the electrical signal when you use your abilities," she said to Barry.

Caitlin dabbed the gel in a circle on his chest before pressing the pad onto it, putting pressure against it for a few seconds. Simmons moved with the same efficiency, and they had the pads placed on his chest, back, and temples in under a minute.

Barry looked between them, and Caitlin thought she heard him say "weird" under his breath. He stood and stretched his arms. "So now I run again?"

"Wait!" Caitlin said. She raced around the room, putting heavy objects on stacks of paper. "We've had to pick up a lot of papers recently," she explained to Simmons.

Simmons nodded, excitement clear in her features. "Alright then. Time for science."

0-0

"Heat resistant, non-conductible metal that's flexible enough to spin in a treadmill." Mack shook his head. "It's a good thing Coulson's still got connections."

"We could make do with a softer material, but this is best in the long-run," Fitz said as they placed another sheet in the loading dock.

Cisco handed them the rope to secure the metal sheets. "It'll be nice for Barry to have something to really let loose on."

"How long do you think it'll take to build?" Mack asked as he knotted the rope on the wall hook.

Fitz pressed the switch to bring the ramp back up, looking over his shoulder at Cisco. "We said a few days earlier, but I think we could be done sooner."

"I had a few more ideas on design last night."

"So did I," Fitz said, somewhat surprised. In all his time working with others in his field (which of course was limited to his education at the Academy and Sci-Ops), he'd never encountered someone as invested in their projects as he and Jemma.

"Any way I can help?" Mack asked.

"An extra set of hands never hurts," Cisco said amiably. "Back at S.T.A.R. Labs, Dr. Wells almost never lets me have extra help. He says it's better for me to learn how to do it on my own." Cisco half-smiled. "He doesn't realize Tess makes sure Caitlin and Barry are always free to help me. It would take way too long to make everything on my own."

"Turbo here doesn't like to admit it much, but he likes the help too."

"Since when have I turned down your help?" Fitz asked in mock offense.

It looked like Mack was gonna crack some sort of joke, but Cisco spoke first. "Turbo?" He had a boyish grin on his face as he looked at Mack.

"Yeah, I like nicknames. I call Daisy Tremors."

"I've got a thing for names too," Cisco said. "Those are pretty good."

"You surprised?" Mack asked.

"Nah," Cisco said. "Just wondering if you can come up with one for me."

Fitz looked at Mack, curious. The man stared at Cisco for a few seconds, then shook his head. "I don't know you well enough yet. I'll work on it."

"We'll have plenty of bonding time building the treadmill," Fitz said, both itching to start building and dreading the labor required for the equipment.

Cisco talked the whole way back to the Playground, prompting Fitz to think of a few possible nicknames. None of them were very good, but they made Fitz have to resist the urge to smile. He would have to share some of them with Jemma later. He wondered how the testing was going with Barry and Caitlin. He probably wouldn't see anyone until that evening. As soon as they got back to the base they brought the equipment to the garage and started finalizing the blueprints while Mack grabbed some of the tools they would definitely need.

It was midafternoon before they started actually building, trading stories to entertain themselves in moments that didn't require particular attention to detail – which was a lot, in the beginning. They didn't get much built that day, but Fitz was extremely satisfied with their progress overall. He was glad Cisco had come back with them.

0-0

Barry peeled the medical pads off his chest and accepted the wet towel Simmons offered to wipe the remnants of the gel off. On his other side, Caitlin handed him another high protein bar. It was uncanny how similar these two were. And he doubted either of them noticed it.

He'd basically done all of the running tests he'd done in the hangar, except slightly more contained. The medical pads had recorded the levels of electricity in his body as he ran. They'd started smoking at one point, so he assumed the levels were high. He definitely felt something different when he used his speed. There was an energy in him, a crackling sensation of energy. It felt good.

Until he crashed to a stop. He'd flipped a few minutes ago, landing spread-eagled on his back, but he hadn't hurt himself. Just embarrassed himself and made the two scientists fuss that he needed to be more careful.

"It's not like I was that coordinated before," he said as he slipped his shirt back on. "But coming to a stop from that speed really brings out my klutziness."

"You've only had your powers for a short time," Simmons said kindly.

"Knock, knock."

Barry turned and saw Daisy standing in the doorway, dressed in black gear. "Hello Daisy," Simmons said.

"You guys ready for me?"

"My part of the assessment is complete, yes."

Daisy walked into the lab and leaned on the table across from Barry. "So you've been running around all day, huh?" Barry nodded, and Daisy drummed her fingers on the edge of the table. "Yeah, I felt like a test subject when I got my powers. Everything became harder, for a little while. It gets easier."

"So I've been told," Barry said, gesturing to Simmons with his head.

Daisy didn't look away from him. "How are you feeling? Are you overwhelmed? Scared?"

Barry shook his head. "No, I'm good."

Daisy continued to study him for a few seconds, and then frowned. "I guess it's a little late for the 'you'll get used to it' pep talk." Her frown faded to show a trace of admiration. "I think you've adjusted faster than I did."

"I had a lot of help," Barry said with a short-lived smile at Caitlin.

"Come on," Daisy said, standing. "Show me what you've got."

"The last part of the field assessment is sparring?" Barry asked.

Daisy started moving. "I need to see how you can use your powers in a potentially dangerous situation. We'll go to the gym, so there are mats you can land on."

Barry jumped up. "You don't think I can win?"

"It's not likely," Daisy said. "Try to prove me wrong."

They reached the gym, and Barry saw that the floor was mostly covered in mats. Mostly, but the edges were tile. He walked to the middle of the mat and faced Daisy, trying to remember exactly what her powers were.

She didn't give him the chance, holding her hand out to send a wave of energy toward him. It seemed like slow-motion though, and he jumped to his right before the energy did more than form near her hand. He watched it go by, felt the air bending towards it, and nodded to himself. So that was her power.

"So you can dodge a basic attack," Daisy said after he avoided a second direct blast and smiled at her. "Why aren't you fighting back?"

"I wanted to give you a chance to show off."

A fiery light glinted in her eyes, hardening them. "You shouldn't have."

Barry rushed her, but she was already moving – which was saying a lot, considering how fast he could go. He reached her and went to flip her, but as his hands closed around her arm, her vibrational attack from her feet caught him center mass. His hand pushed down on her arm before gripping it tightly to stay upright. Daisy used the advantage to bring her knee up and slam it into his stomach.

Barry dropped to the mat as the air was forced out of his lungs. Flashbacks to high school – the last time he'd been in this position, though then there had been a lot more people surrounding him – warred for his attention as he tried to think of a plan to strike back. He had the speed. Daisy had only rivaled it because of how intuitively she fought with her powers. Maybe if he did the same thing…

He moved forward from his low position, knocking her legs out from under her as he rushed by. In the next few seconds he turned and clipped her as he went by, making her body turn as it fell toward the ground. He didn't stop moving, so he could see her start repositioning herself, trying to absorb the shock of the fall in the microseconds she was able to act.

He heard her impact with the mat, but he made a mistake. While he was looking back at her, he was still moving forward. Which meant that, when he did turn to face forward again, he realized he was rapidly approaching the wall. Too rapidly. He tried to grind his back foot into the floor, twisting his knee to flip himself in the opposite direction. He turned, just like he wanted to. Unfortunately, he didn't manage to change the direction his body was moving, and still collided with the wall.

The good news was that, because of his twist, his upper body was spared the impact. The bad news: his leg, which he had tensed and twisted to flip himself, hit the wall at that very wrong angle, and that very high speed. He heard the pop the instant before he felt the sickening pain, and crumpled to the floor as he stopped moving at super speed.

"BARRY!" Caitlin yelled.

He felt hands on his arm, trying to get him to sit up so his leg could be seen to, and it was only as he managed to follow the motions from the hands that he realized it wasn't just Caitlin. Simmons' hands were there as well, just as careful and precise but not as familiar as Caitlin's. Though at this rate, they probably would be soon. Caitlin was by his head, her hand on his shoulder as she peered anxiously at his face. Simmons was kneeling in front of him, her hand on his leg, just above his knee.

"What did you do?" Daisy asked.

"Tried to stop myself," Barry said, gritting his teeth as Simmons touched his knee and a shot of pain lanced through him.

"I'm sorry!" Simmons exclaimed. "But I have to see what's wrong so I can fix it, which may hurt."

"It sounded like something broke," Caitlin said.

"Yeah, felt like it too," Barry confirmed, leaning his head back on the wall.

"Daisy, can you get the -?"

Daisy ran from the room. Barry closed his eyes as Simmons and Caitlin looked at his messed up leg and murmured pre-emptive analyses. He'd been getting scraped and bruised since he emerged from the cocoon, but this was the first time he'd broken something. It hurt more than he'd expected, and he found himself hoping his healing abilities would apply to his bones. He opened his eyes when he heard commotion, and saw Daisy hand Simmons what looked like a tablet.

She held it over his leg and slowly moved it from his ankle up to his knee, and he saw a grimace appear in both of the scientists' expressions. "It's not good, is it?" he asked.

"You twisted so severely that when your leg collided with the wall it… separated the bones." Caitlin said.

"The patella is dislocated," Simmons said, staring at the tablet that must have functioned as an x-ray. Barry didn't know if she was talking to them or just to herself, but she continued. "I've heard of this happening, but I never…"

"He dislocated his knee?" Daisy asked.

"It's not common, and it's supposed to be extremely painful," Caitlin said. "Barry, we might be able to repair the damage right now, but it's going to hurt. A lot."

"It already hurts," he said, looking at the ceiling. "Just do it."

"Do you want to set it back into place, or should I?" Caitlin asked Simmons.

"I'll do it." She looked at Barry with a creased brow. "I'm sorry about this." Then she forced his leg to straighten (sending a wave of agony through him that actually made him cry out) and then braced her hands around his knee. "Three, two, one." She pulled, and another loud sound was heard. Well, was mostly heard. Barry's yell of pain masked it pretty quickly, as did Simmons' cry of "I'm so sorry!" and Caitlin's reassuring "The worst part is over."

Barry took a deep breath as he looked at them, and shook his head. "I don't think the mat helped."

They gave weak smiles. "I didn't expect you to run into a wall," Daisy said, bouncing back the fastest.

Barry's mouth quirked up into an almost smile. "Guess I'm not as ready for battle as you S.H.I.E.L.D. agents."

"You did well," Daisy said seriously. "Aside from the end. You're way ahead of Joey. We can definitely train you up to pass a field assessment."

"For the moment, we should get you to your room," Simmons said. "I'll get you a brace, and you should keep it elevated for a few days, whenever possible."

"If it takes a few days," Caitlin said.

Barry realized the pain was already less intense than it had been. Maybe that meant his body was already healing? He leaned on Caitlin and Daisy as they walked slowly towards his room, Simmons moving ahead to get the brace and meet them there. It wasn't how he'd thought the fight would end, but Barry realized he wasn't discouraged. He'd been doing well in that fight, before he'd had a lapse of attention. It had felt good.

Daisy's words about a field assessment played around in his head, and he found himself looking forward to training with her at the next opportunity. He hoped Cisco and Fitz made a track or something soon. He had some work to do.