Several things were immediately clear to Gellert, chief among them the fact that this man apparently knew him, and well enough to suspect that a design of this complexity could be product of Gellert's own mind, the suffering inflicted on its inhabitants something that Gellert could have found acceptable in the name of scientific progress. Or in the name of his own entertainment.
Yet at the same time, Gellert was certain he had never seen this man before. If he had, he would have remembered. He always remembered a pretty face, even if it belonged to a man who was accusing him of some brand of evil. It was a little bit difficult to balance his suddenly-ignited curiosity with his lingering irritation--because acquainted by this man's standards or not, what right did he have to attempt to confront Gellert in any manner? Gellert already knew how this trial would end--he would be expelled. Expelled, but not arrested, and not punished. If this man was neither a professor nor a law enforcement official, what sort of relationship could he claim that allowed him such benefits? For Gellert was certain that he would never have welcomed any acquaintance at all to be quite so bold.
Gellert stopped walking, deciding in that moment that he would prefer not to reveal to this stranger what sort of locales he frequented before he had a very precise understanding of this situation. He slipped his hands into his pockets, the gesture he favoured for letting his wand slip down his sleeve and into his grasp without drawing notice--realising only after his fingers were already grazing the handle that it was no use here. His magic was worthless. That pounding nausea that had overtaken the voice his magic had left abruptly seemed worse than ever.
"Who are you?" Gellert demanded, seizing onto the man's gaze and keeping his own eyes aloof, unblinking.