"You can't believe everything you hear, Miss Bobbin," he said, following her at a distance. The fact that the devastation was confined to a single room was extremely suspicious.
He'd heard about the virus, vaguely. It was something people discussed quite often, at least when there were more people at the castle. He was certain that if Slughorn was working on a cure, he could be of some assistance. Whether the old fraud would accept his help was another matter.
"Whether or not you're crazy is not something I'm qualified to answer. However, your conclusions in this case are sound. This was undoubtedly a work of sabotage. The question is, who would benefit from the virus not being cured?" he said, the last part more thinking aloud than truly asking her a question.