"Not that I don't," said Stephen, still on-guard but a little unnerved. Well, he did, but there was no need to make things worse than they already were. "Maybe it has," he said, still trying to think of something to ask, something that would prove that he was actually speaking to his friend and not to someone only looking for a chance to cart him off to Azkaban. "But you know - I know I'm a wanted man, for this," he made a gesture with his wand, "If nothing else."
Shaking his head, he continued, "Can't trust anyone these days, I've found." He figured if he was speaking to some random Death Eater, he hadn't given too much away, and if it was Matthew...well, maybe he'd understand. Or perhaps he wouldn't, and Stephen was just digging himself in deeper. "But you have changed. Never seen you cry before, in any case," he paused, trying to think of something. "Matthew...what are the four modern conditions to Tosvig's Constant? And which one's already been proved wrong?"