While the others were talking, Severus mulled over what Potter had said. As little as he cared to give credibility to anything Potter came up with, he thought perhaps his idea was worth mentioning, especially since he was convinced there had to be a specific person or group behind everything that had happened.
"You said you tried to find a specific magical signature," he began, drawing himself up and gazing at Potter with a disdainful sneer, "but did it occur to you, Mister Potter, that there are ways of masking that? Did you stop and think that perhaps it might be more productive to find a magical trail back to its source rather than rooting around for a magical signature?"