"Blood," Briar concludes after her test. "Fortunately for scope of investigation, magnitude of malfeasance, not humanoid. Rodent blood, in point of fact. Killed last night, judging by coagulation, odour, viscosity."

"Sleepwalking hypothesis not impossible, but without any basis in reality. Principle of Occam's Razor (razor reference incidentally well-suited to blood-related query): assume no levels of multiplicity beyond those necessary for answer to question. In laymen's terms: assume simplest answer. Complexity of task to kill a rat, drain its blood, walk to memorial, and draw a symbol on it makes sleepwalking improbable compared with alternatives – vagrants, pranksters, and so forth." She nods vigorously, as if this settles the matter.