Mac explained that they would probably be leaving tomorrow, and then she and Harm turned away. Chloe and her friends deserved this moment alone - to work through what they were to each other, and say goodbye. It was now that Mac expected the gravity of the move to sink in, and she was ready for tears on both sides.

Without looking at the scene, Harm and Mac could tell Chloe had received an emotional response. This no doubt stemmed from the suddenness of the decision as well as its nature. Little enough was actually said, however, that Mac suspected the potential move had been a major topic of discussion in Chloe's group that day. In a bittersweet way, that was a pleasant thought – both Chloe and her friends had had time to come to terms with this decision, which would make it much easier to say goodbye.

It was a cold afternoon, but the spot she stood with Harm was sunshiny enough to make her want to fall asleep on his shoulder. For the moment, the part of her ruled by military regulations prevented more contact than her hand in his, even in civvies. She satisfied herself with tracing circles on his skin with her thumb, closing her eyes slightly and enjoying the sunlight – and wondered if one day she might be confident enough to kiss him in public.

Somewhere in the dark depths of her pessimistic mind, a little ball of sunshine said it didn't matter how long it took. She and Harm had spent most of their lives together teetering on the edge of something, running backwards with pure desperation as the world turned too fast around them. For the first time, they'd escaped the cycle that gave her perpetual motion sickness. They'd landed, coincidentally or otherwise, on the same page of the same book at the very same moment – and she couldn't expect their whole holding pattern to disappear in under a week.

Perhaps, instead of tormenting herself over not being comfortable with more, she should view her hand in his as the achievement that it was. Suddenly, the tracery of her thumb on his skin took on a different dimension. The whole world narrowed to a pinpoint, and the little fleck of contact was all she could see or feel. She embraced it, feeling the tingling under her thumb and the hills and valleys of his calloused hand, drawing a map to his heart.

"Mac," he complained finally. "How do you make holding hands feel so...sensual?"

She tipped her head up, eyes sparkling with honesty where they met his, and said simply "It is."

He shook his head, the side of his mouth curving in the half-smile she loved so much. "You're mad, Sarah Mackenzie."

"You love me," she challenged cheekily.

"That I do."

Preparation for what Chloe dubbed "The Big Move" was a harrowing process. They had to make the trip she'd been putting off, re-entering her grandparents' house and all the memories it held to retrieve her things. She tried to back out a hundred times in a hundred different ways, but as much as Harm and Mac were sympathetic to her plight they both thought she'd probably need the closure. "Chloe," Mac said, "I love you, and I know this is hard – but you know you have to finish to start again." And finally, tremulously, reluctantly, Chloe agreed with her.

And so the trip was made. It was evening by the time they got there, having organised with the government agency temporarily in control to gain entry. Everything Chloe owned, from knick-knacks and toys to old schoolbooks and makeup, went in one of the many carboard boxes. Harm and Mac helped as much as they could, knowing by the shiver Chloe failed to cover as they entered how much of a toll even being in the house was taking. She appreciated their support, even if Harm kept putting stuff in different boxes and "confusing her organisational system." (Harm smirked at this comment, knowing who was the tidy one out of him and Mac.)

They bought Chloe a few bags and coats for good measure, feeling like it was better to err on the safe side when packing for DC. Anything else, they decided, they could more or less get at home. With Harm and Mac packed and all their food cleared out, they were ready to leave in the morning. Harm felt an odd tug in his chest looking around the hotel room he had called home for several days now. He'd got used to the sight of it covered in stuff – Mac's hairbrush on the vanity, Chloe's Nutrigrain on the table, his briefcase on the floor. Now, stripped of their personal touches, it looked oddly empty. Waiting, he corrected. It looked like it was waiting for the next person to use as a holiday, a getaway, or – like them – a transition to a new start.

Mac, Harm discovered, liked to triple-check everything. He'd never been in the house when she finished packing before, and he had to say it was an illuminating experience. He thought she spent more time looking under the beds, in the cupboards, and around the table that morning than he had in his entire life. "We're never coming back here," she muttered when he complained, and frustrating as it was, he had to admit she had a point. It was worthwhile making sure they'd retrieved everything from a place they might never see again.

Chloe was the other end of the spectrum, flopping on her bed with her phone as Mac came in at regular intervals to make sure she'd packed everything. "Charger?" she'd ask distractedly, an odd sock in one hand and a bottle of water in the other. "Yes, Mac," Chloe would mumble, dragging herself away from the screen. "Toothbrush?" She'd question, on her way to put the iron away. "Yes, Mac, it's in the bag," Chloe would repeat. Finally the younger girl begged him to make it stop, and a slightly amused Harm suggested they might be ready to go now. Mac promised she would be in two minutes, and Harm couldn't find it in himself to be annoyed at the endearing sight of her wandering around their "home" with lost belongings and bottles of water, tidying, cleaning and questioning at every turn. (He made sure to be busy whenever she came past, though. Endearing or not, he valued his head.)

The moment they all got into the car for the long drive back to DC felt unpredictably momentous. As much as he'd understood it theoretically before, it was then – with Chloe strapped into the back seat of Mac's SUV and her stuff all around them – that Harm realised she was theirs for now, and probably for good. It was them who were responsible for feeding her, taking her to school, and making sure she was happy. They would be the ones to look after her, organise her birthday parties, pick her up from soccer practice. He reached for Mac's hand, a lifeboat in a perfect storm. This was really happening.

It was afternoon by the time they arrived, and they rode the elevator silently up to the apartment. "Well," Mac said matter-of-factly as she opened the door, "welcome home."

Chloe had spent plenty of time in Mac's apartment before. It was the site of numerous memories – happy, melancholic, and everything in between. But knowing she was living here for now, the familiar rooms looked somehow new. The light hit Mac's little table, where they had eaten dinner on so many nights, and bounced off the sofa – where perhaps, to Chloe's delight, they had eaten just as many dinners. It traced the spot she had been sitting, painting her toenails, when Harm came to tell Mac he was going back to flying. It spread over the windows that looked out across the city – a view Chloe had woken to on perhaps hundreds of mornings. But Chloe knew it wasn't the light that was different, but her perception of it.

With Mac and Harm at her back and her new home spread out in front of her, she was seeing things differently. It felt like a good, comfortable different – and although whether that lasted was yet to be seen, for the moment she was uncomplicatedly happy. It was a spur-of-the moment decision to reach out behind her with both hands, grabbing Mac's hand with one and Harm's with the other.

She didn't need to look behind her to know that their free hands connected. It was a subconscious movement, now, and a giver of strength. Together, they formed a triangle, with Chloe at the head. That brought her mind back to a google query from long ago, typed into the search bar to obtain material for a maths project. "Why," her younger self had asked, "are triangles the strongest shape?" The mythbusters result had popped up in 0.64 seconds: "because any added force is evenly spread between all three sides." That was them, now. She and her new almost-parents, three points that were stronger connected. Any extra load would be spread evenly between them. And something in her was certain that meant they would be okay.