Frowning a little harder, Marcus shook his head as he said, "I am not having this conversation with you. Or with anyone else, for that matter." It was neither a confirmation or a denial, much the way the entire subject was in his own head, and talking about it aloud meant acknowledging it, and he wasn't sure if he was ready for that, and all the repercussions that might come with it, yet.
Squeezing Susan's hand back, Marcus shrugged again, but didn't argue with her. He'd lost track of how many times they'd gone over this, and in the end neither of them were ever able to convince the other. With how dark and depressing the topic was, he was glad to let it drop, because he didn't need to sink into yet another bout of guilt and self-doubt right now.
He wasn't sure if she saw the way his eyebrows furrowed together in confusion at the words, but he filed them away for future reference and didn't ask. As with most things Muggle, asking for clarification would probably just leave him more confused then before the explanation.
Marcus had to admit that he was a little taken aback by the positive enthusiasm of Susan's response. That didn't stop him from unfolding the piece of parchment and laying it on the table in front of them. It was an older sketch of Bryony's, a silhouette of a line of trees with a small flock of birds overhead. Motioning at it with one hand, he said, "I'm just not sure how it would work in relation with... that," another vague motion towards where the Mark was on his left forearm.