A/N: Could have been early S7 compliant at the time, but it's not E13 compliant, if that makes any sense.
A/N 2: Very slightly sad but promising ending? It's not really sad, but it's S7, so they aren't settling into the Perthshire sunset together yet.
A/N 3: Also, the next story can be read as a sequel to this. Or really, a later story in the same timeline. Doesn't have to be, but certainly can be.
Coulson was in the lab watching the monitors for Simmons, when suddenly there was a noise and a shimmering light, and a second later Fitz was standing in front of him.
"Fitz?" said Coulson in confusion. "What are you doing here? And are you real, or some kind of hologram you built into this place that Simmons didn't tell us about? I thought she said we couldn't know where you are."
"I am real, but I was never here. I just urgently need to talk to Simmons. Seen her?" replied Fitz gravely.
"Not recently. When I came in here, she and Daisy were talking, and she asked me to watch the monitors in case something came through, before they disappeared off somewhere. Maybe try you two's bunk — if Simmons isn't down here, and it's not meal time, she's usually been hiding away in there. Reminds her of you, I expect," answered Coulson.
But before he'd finished, Fitz had already disappeared out of the lab and down the hall, towards their room. He didn't pass anyone in the halls to ask if they'd seen Simmons, and soon arrived at their door. Placing his hand on the handprint scanner, as soon as he heard the soft click indicating that it had unlocked, he pulled the door open.
"Simmons?" he called out as he quickly scanned the room, until his eyes landed on the bed.
He quickly kicked the door shut behind him with his foot.
For lying on the bed, sheets bunched around their waists, were Daisy and Simmons, stark naked.
Simmons was lying behind Daisy, so all he could see of her was her head peppering Daisy's neck with kisses, but Daisy's entire front above the waist was visible to him, her perky breasts on full display. They had clearly just had sex, and Fitz froze momentarily, unable to remember when they had ever looked more beautiful — of course, the fact he hadn't seen Simmons in weeks and Daisy in years didn't hurt with that either.
Simmons, meanwhile, had popped her head up in surprise at the door being opened, as no one should have been able to open their door, before freezing herself in shock at seeing Fitz standing there in front of her. As for Daisy, she merely looked at Fitz in slight surprise for suddenly being aboard Zephyr One, not fully understanding just how wrong it was for him to be there.
But Simmons quickly recovered from her shock and jumped out of the bed and crossed the dozen or so feet over to where Fitz was standing, exclaiming, "Fitz! You're not supposed to be here!", before giving him a quick kiss on the lips.
"Maybe pick a different way of phrasing that, sounds like he's not supposed to see us naked in bed having just had sex," came Daisy's amused voice from behind them as she sat up on the edge of the bed.
Simmons embarrassedly opened her mouth to apologize, but Fitz cut her off. "I know what you meant. And I shouldn't. I just realized a crucial error I made with your implant, that the Chronicoms might be able to hack if they realize is there. It's a small chance, but we can't take any risks. Also, I created a couple extra pieces of tech to increase the reliability and security of the communications between us, and wanted to give them to Enoch to install."
While he was talking, Daisy had stood up and crossed over to where FitzSimmons were standing, and as soon as he'd finished, quickly leaned in to give him a kiss of her own. Fitz quickly returned it, before pulling back to look back down at Simmons.
"Yeah, of course," she said. "The implant tool is down in the lab with Enoch, assuming that's what you need. Just let me throw some clothes on."
"So no time to join us?" asked Daisy half disappointedly, half sultrily, as she took his hand in hers and placed it on her naked breast. "It's been weeks."
"It's been a lot longer than that for me," said Fitz quietly mostly to himself, before addressing Daisy directly with a noticeable amount of regret in his tone, "So as much as I always want to join you, I can't be here as long as I already have. But you both look absolutely beautiful, and I want you to both promise me that you'll take care of each other for me until all of this is over."
As Simmons finished pulling her shirt over her head and said, "Of course, Fitz", Daisy smirked, "Oh, we've been doing that all right."
"Daisy…" growled Fitz, as at exactly the same time Simmons exclaimed scandalized, "Daisy!"
Daisy rolled her eyes. "Yes, yes, I'll make sure your precious wife stays safe and sane while you're gone, as well. Now go, scram," she continued, shooing them out of the room. "You have fancy schmancy sciency shit to be doing, that this wife can't follow along with."
Giving her a quick nod of appreciation, Fitz turned and headed out of the room, with Simmons following quickly behind him. A few minutes later they were back down in the lab, with Fitz exchanging several small electrical devices for the communications system with Enoch for the implant device. Coulson watched in interest as Fitz brushed Simmons hair out of the way to reveal the slight orange pulsing of the implant in her brain. Less than ten minutes later, Fitz had Simmons' implant reprogrammed.
"There. Now they won't be able to get around the implant," said Fitz, gently stroking her hair back down over the back of her neck.
"Which means you have to disappear again now, don't you?" said Simmons sadly.
"Sorry, love," replied Fitz regretfully, dipping down to kiss her deeply.
When he finally broke apart, he looked up to find a finally dressed Daisy standing next to them.
"Love you, too," he said as he gently cupped her cheek and gave her a deep kiss as well.
Breaking apart, Fitz stepped back and adjusted the inputs on his teleportation bracelet.
"When will I see you again?" asked Simmons before he could disappear, voice cracking as a tear escaped the corner of her eye.
"You know I couldn't tell you that even if I knew," replied Fitz sadly, cupping her cheek gently in the palm of his hand for a second, before stepping back and shimmering out of existence.
Daisy moved to stand beside Simmons, resting her hand on her wife's shoulder comfortingly.
"He'll make it back. He always does."