Now she knew who he was. Really, it was a relief. They hadn't spoken in quite some time and not many would have retained that information. Jon spoke to so many people each day that he had to work very hard to remember their stories and would sometimes get them confused with another one and he'd have to make up some reason he couldn't remember.
Narcissa had always been nice, from what Jon could tell. No one really had anything bad to say about her. Jon didn't expect it'd do any hard to answer her question.
"During the war, he cast an unforgivable on me," he answered, instinctively rubbing at his chest where he'd been branded. "Long story short, I broke into the Ministry of Magic under his orders and was sent to Azkaban." And now that he'd said it, he sort of wished he hadn't. Why should she even believe him?