Disclaimer: I own nothing you recognise; you know the drill

Feedback: Much appreciated

AN: Sorry about the delay in this chapter; I wanted to wait until I'd seen Thor: Ragnarok so I could determine how my plans for this story would affect things there, and I've got a couple of plans for this and my upcoming few 'epilogue' chapters before I call this story to a halt…

Mercurial

"You're turning a storage facility into your new base?" Barry asked, looking at the large building in surprise. The rest of the Avengers had been fully aware that he intended to go back to his world once the current threat of Ultron had been dealt with, and each of them understood why he wanted to go back, but they'd insisted that he stick around to see what they had planned for the future after everything he'd done to ensure that they'd have one in the first place.

"Hey; it gets the job done space-wise, and it has the advantage of being out of the public eye," Stark shrugged.

"That is important?" Pietro asked.

"We got lucky when we managed to drive Ultron out of the tower before he decided to start attacking the wider area," the industrialist said grimly. "I'm not going to leave this team in a position where anyone else trying to attack us has an obvious target to keep us busy."

"Makes sense," Barry nodded. "Oliver and I have to protect our cities back on my world, but Oliver's always managed to keep his base secret from everyone but the enemies who were more focused on him, and my team keeps our base just far enough outside of the main city so that anybody who knows about me doesn't have any immediate civilian hostages to use if they attack us that way."

"Disadvantage of being local rather than global, huh?" Hawkeye noted.

"It's all got its ups and downs," Barry shrugged, before turning to address the Avengers as a whole. "Seriously, though, it's been good to work with all of you."

"Same," Steve said, smiling as he shook the Scarlet Speedster's hand. "It's been an unconventional experience, but if there's a multiverse out there, it's good to know it has heroes like you to defend it."

"Indeed," Thor nodded, as he followed his leader's example to shake Barry's hand. "You are a noble warrior and a valued ally, Barry Allen; it has been good to work with you in this fight."

"Only regret is that we didn't get to meet more of your guys," Clint noted with a brief smile while repeating his teammates' actions. "Wonder how I'd match up to this Oliver guy."

"Getting competitive?"

"Nothing wrong with that."

"Just didn't expect it of you," Tony shrugged with a teasing smile.

"Who knows what would have happened without you here?" Wanda smiled, reaching over to give Barry a hug as Pietro smiled at his friend.

"Eh, you'd have realised the truth about that psycho robot soon enough," Barry shrugged.

"But you ensured that they realised it before they made more than one great mistake," the Vision noted, a slight smile on his face as he looked at Barry. "Your presence has been a most unique addition to this team, Barry Allen, but one we have all appreciated."

"Yeah," Bruce confirmed, walking forward to shake the speedster's hand, an awkward smile on his face. "It's been… well, like the Vision said, it's been unique, but you've given us a lot to think about."

"Just like you've all given me a few things to think about back home," Barry replied. "I mean, I spent so long being my world's first real hero with powers, and I've only had a couple of actual team-ups with Oliver when things were particularly bad, and now I've seen how heroes can be when they're working together…"

"We have our issues-"

"But you're working on them," Barry smiled at Wanda. "You've made a commitment to be the team that you'll work together to make the world better; that's the important thing."

"OK," Tony said, after the assembled Avengers had spent a few moments standing around in silence. "Now that we've got the emotional sentimentality and heroic congratulations out of the way, shall we just get Barry here back home before this gets too sweet?"

"OK," Pietro said, shaking his head at Tony's antics as he took up position alongside Barry, standing at the end of the largest open area in the field around the new Avengers compound. "How do we do this?"

"We start running, and when I run in front of you, you give me one quick shove and I get the last little boost I need to get back to my own universe," Barry replied. "You ready?"

"Ready," Pietro smiled.

"We'll miss you, Barry," Wanda said solemnly.

"Just remember," Clint added with a grin. "If you ever need our help, you're always an Avenger."

"Thanks," Barry replied, as he placed the tachyon device back on his chest and took up his position alongside Pietro.

Working with these heroes had been an incredible experience, no matter how terrifying it was to face something like Ultron, but in the end, his place was on his Earth.

After taking a moment to pace themselves, the two speedsters leapt into action, charging along the field, energy crackling around Barry and Pietro before Barry moved into position in front of Pietro, the race continuing for another moment before something shoved him in the back. Back in the dimensional breach, he registered a group of people in black leather standing around a large metal room, and a flash of a man in black duelling with a woman in similar attire using blue swords of some kind, before some sense prompted him to slow down just enough…

The distortion effect gone, Barry found himself back on the same street in Central City that he had been on when he originally ran into Kara's world. Quickly falling back into his original pace, Barry took a moment to re-orientate himself and then ran back to S.T.A.R. Labs, through the gate and into the main building in less time than it would take virtually everyone else just to cross the street he'd arrived on.

As he dashed back into the observation room of S.T.A.R. Labs, Barry smiled as soon as he saw his original team sitting at their usual array of computers; working with Kara and the Avengers in the field had been fun, but there was something to be said about the idea of getting the old guard back together, even if he'd only been away for a week.

"I'm back…" he said, removing his cowl and looking around at Caitlin, Iris and Cisco, all of whom were looking remarkably nonchalant at the sight of a man who from their perspective should have been missing for over a week. "How long was I gone?"

"Let's put it this way," Cisco said, walking out from behind the console with a broad grin, "you just annihilated your old record."

"You went four times faster than you have ever been," Caitlin confirmed.

"Four times?" Barry repeated, trying to mentally adjust to compensate for this revelation; if people thought this was still the day of the original tachyon trial- God, it sounded like they all thought he was still taking part in the trial- he must have… pulled a Narnia or something and come back to his world pretty much the moment he left it…

Then Harry Wells came in to confirm that his current speed was greater than Zoom's, and Barry forgot all about that particular issue; right now, his time with Kara and the Avengers was just a pleasant memory, whereas Zoom was a clear and immediate threat that had to be stopped ASAP.

AN 2: There will be a bit of a jump for the next chapter as we go straight to the second season finale of Flash, for reasons I'll explain then, but if all goes well, I think you'll like what I have planned