Consider, Reader, a boy.

He is young, he is foolish, both in the ordinary way of young boys and in other, more intriguing ways.
Intriguing, at least, to the woman. She is not young, not foolish. She is, in fact, six-and-thirty, and a scholar of some repute.

At first he does not stand out among the legions of boys she has taught, except perhaps by his singular lack of boyish appeal. At eleven, most boys still possess a glimmer of it, a late-summer moment of sweetness before they succumb to too-knowing adolescence.

But we change things by our observation. So perhaps what eventually becomes of the Snape boy can be laid, in some small measure, at Minerva McGonagall’s door. Or perhaps not. She will ask herself the question later, when she is restless in the night, in the too-large bed that is the privilege of the Head of Hogwarts to occupy, alone.

But for now, let us regard him as he first appears to the professor when he trudges up to the dais and seats himself, skinny legs dangling, on the stool to be Sorted.

He is short for his age and too thin; we can see that, even under the patched black robe that ill fits him. The impression his face gives is of a bird—a raven, say, with a cruelly pointed beak, beady, black eyes, and shiny, ebony feathers. The feathers, to continue the metaphor, are a bit scraggly, and it would appear that the boy has not had benefit of a skilled barber in some time. There is a smattering of pimples on his forehead, simultaneously announcing his approaching sexual maturity and dooming it to furtive, onanistic fumblings for its gratification.

Turning from the unfortunate facts of his appearance, we move on to more subjective observations. He is afraid; oh, yes, there is as much fear in him as in any of the dozen-odd children who have accompanied him this far, but he makes a greater effort to conceal it. He is betrayed by the gripping of his hands around the rails of the stool—so tight that the teacher can see his knuckles turn from sallow-tinged pink to bloodless white. His legs do not kick excitedly in the way of many children who have been seated here, but hang lifelessly down, waiting for the judgement of a sentient head-covering to set him on the next steps toward his destiny.

His face is fixed, his lips pressed into a thin line so unmoving that one could use it to measure a few inches of parchment, were one so inclined.

None of this is particularly remarkable. The teacher has seen his ilk before. He is a fierce little thing, she thinks, much as she herself was at the same age, but such intense children do come along once in a while. What captures her interest, as she looks down at the child perched on the chair while the seconds tick inexorably by, is that he does not blink. When the Hat finally renders a verdict, he does not look at her when she congratulates him.