Potter recoils the moment the spell leaves Snape's mouth. He throws a hand up, as though to deflect a blow, and stumbles backwards, catching the corner of a desk on his way down and hitting the floor with a crash.

Snape strides out from behind his own desk and stalks toward the sprawled form of the boy, anticipation urging him on like a fierce hunger. It can only be an expelling offense, this secret, for the boy to go to such lengths to protect it, which means that for Snape this moment borders on apotheosis.

Potter lies on the floor, curled in on himself with his back turned to Snape. He watches as the boy presses a hand to his face, and flinches.

Then, before Snape can take another step forward, Potter scrambles to his feet and begins to run for the door. Snape watches him scurry, amused and mildly insulted, but does not stop him until he reaches the exit. A lazy flick of his wand sends the door flying shut in the boy's face, nearly catching his fingers.

Potter stands facing it, shoulders heaving with his ragged breath. He stands still for a moment, then his hand seizes the handle and rattles it furiously. Snape's amusement deepens—he must be truly desperate if he thinks for a moment that Snape's wards will be broken with such a childish gesture.

He takes his time advancing on the boy, savoring the moment as the distance between them shortens. When he comes to a stop a few paces behind Potter, the boy's shoulders hunch, and he seems to grow visibly smaller.

"Look at me, Potter."

But Potter does not move.

"I said turn around, Potter! Or I will call the Headmaster."

When the boy still refuses to obey, Snape decides this is all the excuse he requires. He reaches out and seizes the boy's shoulder, ignoring the gasp this elicits, and turns him forcibly around, driving him back against the wall as he does so.

And then they are face to face, and Snape lets him go abruptly, snatching his fingers back as though they have been burned.

Potter's head is bowed; he is staring at the floor as though in hopes it will open and swallow him. Snape can nonetheless see what the glamor was hiding. It is...not what he expected.

He is too taken aback even to cover his shock with a curt word or gesture.

The left side of Potter's face, from brow to ear to chin, is one solid bruise, or rather a mass of several bruises of varying ages. Some are older and yellowing, others still purple and dark. His lower lip is split and swollen, leaking blood, mirroring the neat gash on his forehead over his right eyebrow.

Snape takes a deliberate step back to get a clearer look at the figure in front of him. Now he can see long narrow bruises in the shape of fingers at Potter's throat, half concealed by the gaping collar of his shirt. He suspects, with a thrill of dark knowledge, that the bruises do not end there.

Badly disturbed, Snape still manages sufficient control over himself to sneer when next he speaks. His heart, however, is not quite in it.

"Brawling on the school train, Potter?" he asks, though he already knows the answer.

"No sir," mutters Potter, still gazing at the floor.

"Then explain this."

The boy's reply is so quiet he cannot decipher it. "Speak up, Potter."

"I said, sir, that I'd rather not discuss it." And then he does look up, and Snape is startled by the expression in his eyes—equally pleading and defiant. "I haven't broken any rules."

"You do so in failing to answer my questions satisfactorily, Potter."

"Then give me detention!" Potter shouts, and winces in the next moment, touching his fingers to his lips as a fat drop of blood appear at the corner of his mouth.

Snape gazes down at the boy, hands balling into fists at his sides, torn between doing precisely as Potter suggests, if only to vent his own frustration, and offering the boy a handkerchief.

But he does neither of those things.

"Why would I give you detention?" he inquires silkily, taking a step forward.

Potter's back is against the wall, so he cannot get any farther away, but he flinches at Snape's approach. Snape stops where he is—something in that flinch disturbs him, warns him that he is nearing a line he does not truly wish to cross. "Why," he continues, "would I subject myself to hours of your company, when can I simply summon the Headmaster and allow him to deal with your—problem?"

He recognizes the wild look in Potter's eyes as panic. "Assign me to Filch, if you don't want me," he says quickly, in a voice that trembles too hard to sound like anything so insolent as a demand.

There is something in that display of fragility that causes Snape's patience to finally give way. "I want answers, Potter," he snaps, "and I will have them from you—one way or another."

He raises his wand level with Potter's face, and watches the boy's eyes widen. Potter apparently does not realize that if he Legilimizes a student without Dumbledore's permission he will be in more trouble than even Potter is worth, and for a moment Snape enjoys the sensation of having regained the upper hand.

"Don't!" says Potter wildly, not quite shouting. "I can't—sir, please don't."

It is the hopelessness behind the plea that has Snape lowering his wand, more than anything else. Something about the tone of his voice causes Snape to suspect that Potter has said "please" before, in that same desperate tone, and been ignored.

They stare at each other for a long moment. Then Snape exhales loudly, pinching the bridge of his nose.

"I cannot debate this with you all afternoon, Mr Potter," says Snape, in what he hopes is an even voice. "Nor can I simply let you go," he says, cutting the boy off even as he opens his mouth. "The teachers of this school are entrusted with your safety, and I will not incur the Headmaster's displeasure by—"

"He'll never know," Potter interrupts. "I swear it. Professor Dumbledore is the last person in the world I want to find out."

Despite himself, Snape laughs. "You foolish boy," he says easily. "Do you really think anyone in this school can keep a secret from Albus Dumbledore?"

The flush along the unbruised portion of Potter's face is just as he expected, but the words that follow are not.

"If Professor Dumbledore was really all-knowing, this would never have happened in the first place." His mouth tightens. "Or else he is all-knowing, and he doesn't care. Either way, you're off the hook."

Snape ignores the cold suspicion that washes over him at the boy's pronouncement."Mr Potter. I am not trying to get myself 'off the hook,' as you put it. I am trying to help you."

"Why?" Potter's voice is very nearly shrill. "I already told you, no one's going to think the less of you. I'll just reapply the glamor, no one will notice. No one ever notices!"

No sooner has Potter finished speaking than his mouth drops open slightly, then shuts in a firm line. He closes his eyes too, screwing his face up tightly. He has obviously said more than he meant to, and suddenly Snape finds it easy to pity him—that last phrase alone has told Snape nearly everything he needs to know.

A heavy weight seems to settle on his shoulders, then—a weight approximately equal to that of a frightened, injured, angry sixteen year old boy. He tries to shrug it off.

"This is not the first time you have come to school hiding injuries beneath a glamor, then?" he says calmly. "Dumbledore has you wrapped up tighter than a maiden's virtue during the summer—you go nowhere he does not allow, and he allows you nowhere but your relatives' home and the Burrow. Yet your injuries would have been treated, and no doubt avenged with deadly force, if Molly or Arthur Weasley had seen them, so I am left to conclude that you obtained them while in the care of your Muggle family."

He pauses, looking for some kind of reaction, but all he gets is a slight twitch of the boy's shoulders at the mention of the Weasleys. He presses on.

"None of your injuries have been treated; there are newer bruises layered over the older ones, and you cannot have hidden them with a glamor during the summer or you would have been up before the Wizengamot for the second year running on charges of under-age magic use."

Potter's eyes remain closed. He has turned his face away, a flush once again rising from beneath his collar.

"So that leaves just the one question, Potter."

The boy still does not acknowledge him. Snape takes half a step forward, and when he speaks finds that his voice has gentled, almost unconsciously.

"How often does it happen?" he says quietly.

There is no response.

"Harry," he tries again.

Ha, Snape thinks, triumphant, as Potter's eyes open and he turns around to stare up at him. Thought that might fetch you.

"Please stop," Potter whispers.

"I already told you, I cannot—"

"I mean stop acting like you care about me!" The boy's hands are clenched into fists now, his voice quiet, shaking with all the effort he is exerting to keep himself under control. "Please, sir. It just—it makes it harder."

Snape's brow contracts in honest confusion. "Makes what harder?"

Potter covers his face with both hands, pressing his fingers to his eyes. When he speaks, his voice is muffled. "I have to act like nothing's wrong," he says. "If Dumbledore finds out, he'll send me somewhere else, away from the wards, and I won't be safe. Voldemort will get me, or my friends. And if he doesn't send me somewhere else, then I'll know that he knew all along, and he still let them—" His fingers clench, so hard Snape knows that he must be pressing them into the bruises, causing himself deliberate pain. "I have to pretend it's all fine, or people will die, like Sirius, and I can't keep pretending with you standing there, acting like you care, when I know you don't, you've always hated me—"

Snape watches, horrified, as Potter's knees buckle underneath him and he collapses to the floor, sliding down the polished wood surface of the oak door with a whispering sound. Potter reaches out to balance himself with his hands, revealing a face smeared with tears and blood from the cut over his eyes.

Before he quite knows what he is doing he has sunk to one knee before the boy and reached out with both hands to steady him. Potter meets his eyes, more surprise in his expression than Snape finds flattering, and Snape—

He should leave. He should sedate the boy and floo for Pomfrey, or Minerva or Albus or all three, and have done. He would be out of his depth in this situation even if it were a student of his own House, one he hadn't been at bitter odds with for the last five years.

But he doesn't turn away. His grip tightens on Potter's arms, until a hiss of pain from the boy and a backwards wrench of his shoulder reminds him that, whatever happens afterwards, there are problems here that do have solutions, many of them in potion form.

"Stay here, Potter," Snape says, and gets to his feet, feeling suddenly very tired. "I will be back in a moment."

He could simply summon the necessary potions from his cabinet, of course, but he wants a moment alone, a moment to gather himself and think what on earth he is supposed to do with a Harry Potter who is desperate rather than defiant, a Harry Potter who suddenly reminds Snape much more of himself at his own age than he ever believed possible.