"But," Darke went on, "we're dealing with someone who specializes in undercover work—infiltration, disguise, and escape. Mercury is far more dangerous than you realize." Darke's black eyes seemed to look into Roxborough's mind, measuring him molecule by molecule. "Mercury doesn't tit into the statistical models, Roxborough. He lives in the extremely slim margin outside the numbers. I told you he worked for Dunkelzahn. Did it occur to you that a dragon's lair might have a protective circle powerful enough to block the ritual detection?"