It's wrong. It's all wrong, but it's proper. It's proper, and therefore it should feel right, but it doesn't.
For starters, Horatio shouldn't be above anyone: it was never like that, whichever way they tried, because it couldn't be – not without bringing up memories better forgotten – so it's strange to have only cold air at his back, rather than the familiar warmth of a cheap mattress.
It's strange, too, that the lips against his are soft and gentle; lacking both the wind-chapped firmness and the determination to muffle noise made by either party that used to be so familiar.
The slightly breathy sounds she makes are too high; too uninhibited. Her fingers are too careful against his skin; too smooth. The sense of urgency there often used to be is missing. There isn't even the reassurance of the teasing little nibbles along his clavicles that had begun as a distraction from the less pleasant aspects of inexperience and become a regular occurrence once it became clear that he enjoyed them immensely.
Still, there is one thing that's almost right – there's a genuine affection in her actions towards him. If only it was reciprocated, perhaps Horatio could ignore the differences. But it isn't…at least, not in the same way; so he closes his eyes and recalls soft sky-blue and coppered gold, and the warmth of the love he found there.
Afterwards, it's vaguely pleasant not to have to get up to open a window before turning in. That doesn't make up for the lack of angles on the body curled against Horatio's own, but it's something to be positive about in amongst the wrongness. Even the smell is wrong; laced through with faint floral undertones from the scent Mariah was wearing earlier. Perhaps, Horatio muses, it is as well he is returning to sea on the morrow – he can blame the anticipation of action for his difficulty sleeping, and nobody will question it.
I would note at this point that Horatio and Archie wouldn't have needed to cover up just sharing a bed, because that was fairly normal practice at the time, especially amongst somewhat-impoverished sailors. That is all. Thanks for reading :)