When he gives his word that he won't harm her, it's less a promise to her than to himself.

He won't. He won't.

The fact that her anxiety no longer perfumes the air is almost entirely irrelevant to his offer of a jacket, beyond that of a convenient excuse. He needs to mark her somehow, the moulding of his scent to her is the closest satisfaction to hand. He cannot, will not, hunt, and this game is not running the way it ought.

(Thank God; it's a prayer he does not often mouth so long and far from where he began, but thank Him nonetheless).

It's a demonstration even human's recognise, so there's no excuse – none – when Marcus thinks, dares, to breathe her scent with such intent. The boy (he'll always be to him, despite the breadth of time that links them) is a born trickster, with an impish turn of mind that has, too frequently for his age, brought trouble. He is, then, well-versed in distinguishing the moment a prank has gone too far.

Too close, too close by half. This impulsive son may occasionally like to take a tiger by the tail, but he has not survived so long by not knowing when to drop it. He backs off quickly (not quick enough for the hackles that rise in the edge of Matthew's teeth) and sees too much, his speculation following them around the lab like a moth to a light as the truth of their research is laid bare.

(Miriam's eyes miss nothing, but she knows better than to poke at this particular beast).

The movement of Diana away from the pair calms his instincts some, but not enough to stop sending a flash of warning back over his shoulder. He's being too obvious, the puckish curl at the side of Marcus' mouth proves as much, but the warning is heeded regardless and they retreat further.

Later, sunlight warming them as they stroll through the grounds, there's no reason for the jacket to remain, but it does, and so does the satisfaction of seeing it there, a tangible symbol of as-yet unspoken thought. He will not harm her – nor will any other manner of thing. A truth to add to the pile of the day, a protection further afield than the sturdy grey cloth draped around her frame.

When she gives him his first glimpse into the manuscript he's been hunting for so long, he gives thanks. But when he takes the fragile sinew of her wrist, pressing his lips to the delicately throbbing cover of skin – magic is desire made real – he gives less a promise to her than to himself.

I will not harm you. Will not. You are in my keeping.