When Robin wakes for the second time that morning, she's conscious of two things. One is the sun, bright light searing the back of her eyelids and warmth spreading over her.
The other is that she's being watched.
The panic that would usually clutch at her stomach doesn't come; the sensation curling up her insides is a different one entirely. She stretches, luxuriating a little in the warmth.
"What?" she asks, half opening her eyes.
"You sleep on the other side," he says, matter-of-factly.
Usually, she's up first, ensuring she's in the office before Pat arrives. But today Strike has an early client and she's working late, so this morning he's the one showered and buttoning up his shirt, crutches propped against the chair.
"I moved over," she answers, "You had all the sun."
He shakes his head. "At your place," he persists, "The watermark on the bedside table my side. It's your side usually, isn't it?"
This is the downside of dating a detective.
It's not the only downside, she's learnt, this past month or so. The way he almost always leaves it to her to decide where they're going out ('but you're better at it', he argues). His peculiarly competitive approach to ironing ('army hangover', he says, though her favourite jumper hasn't looked quite the same since). The times he shuts himself off, like he's carrying around some burden that's not hers to know about (Matthew was always talking about his feelings, with disregard for her own).
"It's a habit," she says, self-consciously smoothing down the sheets she's pulled right across to that familiar side.
Last night's stay over was planned, and she's rewarded with sheets fresh with detergent, as opposed to the unplanned nights when it's more often the lingering smell of cigarette smoke - another thing she doesn't love, exactly.
He reaches for his prosthesis.
"I can swap. I've done it before."
"Of course you have," she returns, before she can stop herself.
It's still awkward territory, the discrepancy in their relationship history.
He doesn't say anything, a tactful retreat something she's learned he does pretty well.
"You're right," she begins, filling the silence the way she's watched so many clients do, met with the same. "This is my side; it's always been my side. But I can change." She glances over to the window, shielding her eyes against the glare. "I'd like to."
He still says nothing, but he's stopped what he's doing and she feels his focus fixed on her, the same attention that keeps clients talking and that he's always afforded her.
"It's just - different."
She doesn't know how to say what she wants to say. That switching sides wasn't just for him: mostly, it's for her. That the old side belongs in another life, and that the one she's stepped into fits her in a way that one no longer could and never really did. That everything is better, and grounding herself in frustrations and small things brings home that it's real: not a new beginning - they stumbled into that, literally, long ago - but a new chapter, and a good one.
"It's different for me too," he says, simply.
Five words that sit there, sunlight flooding the room as Robin basks in it, the weight of that past that doesn't include her dispersing like the motes of dust it catches.
It's not being watched that gets her, she thinks. It's being seen.
"I should have known, though," he adds, a grin suffusing his face. "We've always been on the same side, you and me."
She laughs.
He heads across and picks up his watch from the bedside table, the side that she's still occupying.
"How long?" she asks.
"Got twenty minutes yet," he answers.
"Cover me later," she says, "I've got to do the walk of shame. Do you think they know?"
"Honestly? I think they pre-date this." He grins. "By months." He looks down at her. "I'll cover you. Although, for the record, you're good uncovered, too."
She feels that same smile steal across her face, hair falling in her eyes as she shifts over, irresistibly rumpled like the sheets that she means to pull with her, but they're suddenly weighted down.
He turns towards her.
"And you know, if it gets weird, you can come over to my side any time you like."