Severus Snape, smirking, helped Madam Pomfrey to lay out rows of sterile silver needles. Each needle shone in the morning sunlight that washed through the infirmary windows, and an echoing spark flashed in Snape’s eyes. It was time for the sixth year students to receive their vaccinations and Snape had, as always, been drafted to help Madam Pomfrey after another session of fending off Dumbledore’s lemon sherberts and offers of tea.

Perhaps Snape had required less persuading this year than he had in past years. Perhaps he had declined only six lemon sherberts and three cups of tea before acquiescing to the Headmaster’s suggestion that Madam Pomfrey needed help with the sixth year vaccinations. Snape was, after all, a painstaking Potions Master and knew that his presence was required during the vaccinations in the event of a student reacting poorly to the treatments. His easy acquiescence to Dumbledore’s request had nothing, therefore, to do with the fact that this year, the Gryffindor Golden Trio would report to the infirmary and submit to the sharp silver needles of Madam Pomfrey – nothing at all, or so Snape told himself.

Snape smirked as he arranged the vials of vaccinations in precise rows. Viscous green, clear, pale blue, a rosy tinted liquid that resembled the Golden Gryffindor’s insolent smile – the potions shone in the sunlight. Potter had missed the fourth year vaccinations due to the Triwizard Tournament and would receive the shots he had missed today. Ten vials for him, ten sharp needles – Snape arranged the supplies with care, setting aside the ten sharpest-looking needles for his least favorite student. Snape’s severe black robes fluttered and flapped as he paced the infirmary, stalking down the row between the neat white beds. It was lunch time – they would call the students into the infirmary soon – he would have Potter at his mercy soon.

The students were summoned in alphabetical order. Snape suffered through the usual mix of flinching dunderheads. He took no pleasure in their reaction to the painful prods and many injections. He was waiting for Potter.

At length, Potter came. Snape’s patience was rewarded – the Golden Gryffindor, at his mercy. He vowed to suffer through three teas with Dumbledore without complaint to thank the man for giving him this golden opportunity. Potter entered the infirmary, tentative and shy – as though it wasn’t his second home, Snape snorted. “Madam Pomfrey? You wanted to see me?” the boy asked.

“Yes, Mr. Potter. Have a seat on that bed. We’re taking care of all your vaccinations today,” she said, bustling over with a tray. Ten vials, ten sharp needles – Snape gloated.

“Vaccinations, Madam Pomfrey?” Potter said. Snape sneered – the boy had the intelligence of a parrot.

Potter jerked back as Pomfrey swabbed his arm with ethanol. “Madam Pomfrey, what are you doing?”

“Your vaccinations, Mr. Potter,” she said. “Surely you’ve had some before. It won’t hurt a bit if you just hold still like a good boy.”

“I haven’t had them,” Potter said. His protest was evident in his rigid posture, his panic was evident in his green eyes. “Why do I need them? Surely I’ve gotten by without them before. You aren’t going to stick those needles in me, are you?”

Snape smirked. This was even better than he had anticipated – the glowing Gryffindor afraid of a few pokes with a needle. He could circulate this story among his Slytherins and make Potter’s life miserable for a few weeks at least. “Surely you aren’t frightened by a small little needle, Potter?” He mocked the boy as he filled a syringe with the viscous green potion.

“We should update the boy’s Muggle vaccinations as well, shouldn’t we, Poppy? After all, we don’t want our precious little Savior to come down with a nasty illness.” Snape said.

“I don’t get sick,” the impudent boy said. “Ask Hermione – she – we - no, you don’t understand,” he said. He yelped as Snape, who had lost patience with him, injected the potion into his vein. Potter jerked back from Snape and glared at him. “You can’t do this to me – that hurt and I think the vaccinations aren’t good for me.”

“On the contrary, Potter, they are good for you. You are simply a spoiled little boy who’s been given his own way for far too long. So you persuaded your relatives that you didn’t need any vaccinations – putting them at the risk of disease because you were too selfish to suffer through a few pinpricks? What a letdown to Gryffindor courage you are, Potter.” Snape sneered at him. Having the second needle prepared, he jammed it into the boy’s vein without warning. The sensation of the needles piercing Potter’s skin – Snape gloried in it. Indeed, he would sit through four teas with Dumbledore without complaint, to thank him for this opportunity.

Then – in the severe white infirmary washed with sunlight – Potter jerked and trembled. His eyes trembled open and shut in small rapid motions. Potter fell to his side on the bed, and one leg kicked out as he sprawled, helpless, on the bed. Potter moaned. “Hermione – get Hermione – please, Professor, please.”

Snape sneered at the boy’s outburst, convinced that he was faking a reaction in order to avoid the sharp needles. “Get up and stop moaning, Potter,” he said.

Pomfrey, meanwhile, was casting several diagnostic spells. She trembled and put her wand down, letting it clatter against the tray on the bedside table. “Severus, you’d better fetch Miss Granger,” she said. “It seems that Mr. Potter is having some sort of severe reaction to the vaccinations and she may have an explanation. I don’t know what else to do – his heartbeat is erratic and I think his organs might be on the verge of shutting down.”

Severus stared at her, aghast, for a full moment before running out of the infirmary. His black robes fluttered behind him as he sprinted to McGonagall’s classroom. The halls were empty. His footfalls echoed in an uneven palpitation – much like Potter’s heart, Snape thought. What had that foolish boy done this time?

“Minerva,” Severus said, gasping. His lungs felt too small for his ribcage and his face felt hot and swollen. “Miss Granger is needed in the infirmary, it’s urgent.”

The girl rose from her seat without looking at her professor and came to the classroom door. Next to the panting Potions master, she was small and white and worried. “Professor? Is it Harry?” she asked.

Snape did not answer, only took her arm and pulled her down the corridor to the infirmary at a run. There was no yelp of protest from her, although Snape’s fingers were wrapped tight around her forearm.

Pomfrey was pacing next to Potter’s bed. She held her wand with both hands as though afraid to use it. “Severus?” she said. “Harry wasn’t allergic to any of the ingredients – I checked his file. I don’t know what’s gone wrong.”

Granger fell to her knees next to the bed. “Did you give him the vaccinations? I told him not to let you do it – did you?”

“He had two of them, Miss Granger – the one against Wizard’s Flu and the one against Dragon Fever,” Snape replied. His breath came in short gasps, his lungs still felt too small, but he had regained his presence of mind. “Why is Potter reacting negatively to the vaccinations?”

Granger, irritating chit that she was, ignored his question. “Madam Pomfrey, I need him to be conscious – can you do that with a spell? I don’t think he should have any potions right now.”

“Ennervate,” Pomfrey said, her knuckles swollen from gripping her wand tight. Potter stirred and moaned and flung one arm away from his curled position on the bed. Granger grasped his wrist in one hand, the other she touched to Potter’s cheek.

“Harry? Harry, can you hear me?” She didn’t wait for a response. “Harry, listen to me. Professor Snape accidentally injected you with a sort of poison, Harry. You need to get it out of your system for you to be healthy. You need to focus now and work on pushing the poison out of your body, Harry – do you hear me? Focus on pushing it out.” The boy shifted on the bed as though uncomfortable. He moistened his lips and then caught the bottom lip between his teeth. “Focus, Harry – I know you can do this,” Granger said.

In the background, Pomfrey murmured diagnostic spells, her hand still gripping her wand too tightly. Standing close to Snape, she spoke in his ear. “He may not make it, Severus – his heartbeat is too erratic and everything’s just – just giving up.”

Snape’s lungs, his breath, his heartbeat, the blood flowing through his veins – it all stopped as though an Impediment Curse had been cast on them. Potter – the Gryffindor Golden Boy, the future savior of the Wizarding world – could he die from a few vaccinations? Could it be that he, Severus, in his spite and malice, delighting in the boy’s pain, had killed him? He reached out and grasped the bed railing, held onto the cool smooth metal for support.

Granger’s voice turned sharp, pointed like the needles laid out in shiny rows. “Harry, listen to me now, listen to me. You can’t give up like this – you have got to push the poison out of your body. If you don’t,” here she paused and looked back at the two professors for an instant, “If you don’t do it, Harry, they’ll send you back – they’ll send you back to the Dursleys, they’ll take you away from Ron and me. Do you want that to happen, Harry? Do you want to let us down like that? Push the poison out of your veins, Harry.”

Just as Pomfrey reached down to pull Granger away from the boy, out of the pool of sunlight where she knelt, a spurt of liquid emerged from the spot where Snape had injected the needle into the boy’s arm. The liquid was rosy pink and made a graceful arch before it was sucked up into the syringe from which it had come. A few seconds later, the viscous green potion also emerged from Potter’s arm and oozed, like a slug, into the other syringe.

Snape watched, astonished – how was it possible that the boy had separated the two potions from his bloodstream, filtered out the tiny molecules from the rest of his blood? What kind of power, how much strength, had it taken? Snape did not know any other wizard capable of the complex delicate task that Potter had performed. As though the clean sunshine the washed the white infirmary walls had burst into his brain, Snape believed that the boy lying helpless on an infirmary bed might yet be the Savior that the wizarding world expected him to be.

Potter was pale, his skin clammy to the touch. His sooty eyelashes fluttered twice, but his eyes remained shut. Granger, still kneeling beside him, pressed several kisses onto the hand that she had been holding. “It’s okay now Harry – it’s going to be okay – you can sleep now,” she said. “You’re safe here with us and they won’t take you back, you can stay with us now.”

Pomfrey, bustling around the bedside with diagnostic spells and healing spells, announced that the boy’s heart rate was normal. She smoothed back a lock of the boy’s messy hair away from his face and remarked that he’d better stay in bed for a few days after a scare like this. Snape snorted – the boy would be lucky if the infirmary didn’t become his official home.

“Well, Miss Granger,” Snape said, drawing himself up to his full, impressive height and looking down at the seated girl, “I do hope that you can provide us with a satisfactory explanation for these events.”

They were in Pomfrey’s office, where she was passing around tea and biscuits – “just a little something for the nerves, something to calm us down after all that fright” – and Snape was determined to extract explanations from the Granger girl.

“Sir,” she said and then paused. “I – I don’t know that I have an explanation, and really a lot of it is Harry’s business, things that I’ve promised not to tell.”

“I think that our concern for the boy’s health should outweigh some petty schoolyard promises,” Snape sneered. The light that came in Pomfrey’s office windows turned the girl’s hair golden, almost a halo. Her skin was pale and it seemed that she hadn’t quite caught her breath back – in other words, easy to intimidate.

“I only have a theory, really,” the audacious girl said, as though she hadn’t read half the library before theorizing. “But it seems as though Harry’s done something to his immune system – probably some accidental magic when he was younger. He never gets sick – oh, I know he’s in the infirmary a lot, but that’s always for accidents or mishaps or things like that. I’ve known him for six years now and he hasn’t gotten sick once. It’s … well, it’s really not fair for me to tell you any of his secrets while he’s lying out there unconscious.” Her teacup trembled in her hands and she set it in the saucer. “I really should go out and sit with him.”

“Miss Granger,” Snape leaned closer to intimidate her. “I don’t believe that you’ve given me a satisfactory explanation at all. Sit down,” he said. “What sort of change do you think he has made to his immune system, and why? If it is the product of accidental childhood magic, then why do all children not produce such an effect?”

“Professor Snape,” the pale girl said, “With all due respect, I really can’t tell you anything more without violating Harry’s privacy. There are things that he doesn’t want anyone to know, and I can’t tell you.”

“Granger, you are an insufferable know-it-all and for once – for once in your life, you are unwilling to share that knowledge with the entire world? I don’t believe it,” Snape sneered, his patience gone. “You will sit in that chair and you will tell me why the vaccinations produced this negative result or, Merlin help me, I will march straight out there and give the Potter boy the remaining injections. I don’t have to accept this silly theory of yours that he has an altered immune system – it was probably a result of those two particular vaccinations being combined, and he won’t have any trouble taking the rest of them.”

“Severus,” Pomfrey gasped, but he gestured for her to be silent.

“Which is it to be, Granger? Will you tell me the truth, or will Potter be vaccinated?”

The fiery Gryffindor spirit was not cowed – in fact, such a challenge was more likely to provoke it to flare. “I don’t believe you’d do that – not even a cruel, sadistic man as you are – you wouldn’t risk Harry’s health like that – not when you know that he’s the one who’s going to save us all from You-Know-Who,” she said.

Snape dropped into the chair opposite her. “No, Granger – I do have a conscience and I wouldn’t give those vaccinations to your precious little savior. But if I do not understand why he had this particular reaction, I – or Madam Pomfrey – may someday give him something that will provoke another reaction. You may not be there to save him then, girl. You can keep your promise to the boy, or you can give us information that may someday save his life.”

“Hermione,” Pomfrey interjected, “Professor Snape and I, as medical professionals, are bound to respect the confidential nature of whatever you tell us. Harry’s secret is safe with us – we wouldn’t use it against him or ever tell anyone else.”

Granger looked down at her hands and fidgeted. Snape noticed that her nails had been bitten to the quick and were rough and unpolished. “All right,” she said. “All right. Harry was – he was sick once. He was four years old and he had some sort of infection – he barely remembers this, and he didn’t really want to talk to Ron and me about it, so I don’t know what sickness he had. The Dursleys laughed at him for being sick, they didn’t give him any medicine – they shut him in his cupboard and punished him for being sick, okay?”

She paused, her breath rattling in her throat. She folded and unfolded her hands in her lap, fidgeting. Snape breathed in and out, slow deep breaths – he would be patient. He would not react to the sob story, the Gryffindor legend that their Golden Boy was abused and tormented and, like a miracle, rose out of the abuse and mistreatment like a phoenix from the ashes. He had heard these stories before – stories about the boy locked in a cupboard in the dark – heard and disbelieved and protested – but now, he found that he had no protests. Clenching his fists in his black robes, he remained silent.

“You – you don’t understand, I don’t think I understand, what that did to him. He’d seen his cousin Dudley get treats and medicine and every sort of care and attention when he was sick, and Harry thought that since he was sick, he would get the same – only he didn’t. Ever since then – Harry hasn’t gotten sick once. None of the normal childhood diseases, he never gets the sniffles in the winter.”

“I don’t know what he did – accidental magic obviously, I know he was doing some by that age. There isn’t any reference to anything similar in the library, but if you work out some Arithmancy equations – oh, I left the parchment in my bag in Transfiguration – anyhow, it seems to predict that Harry’s changed his immune system somehow and that it isn’t compatible with the vaccinations anymore. I think – I’m not an expert in Muggle medical science, but my parents know a little bit – I think that his body recognized the vaccinations as being foreign and started a violent reaction against them.”

“How did you know what to do? How did you know how to talk to him to bring him out of it?” Pomfrey asked.

Granger looked at her hands again and her cheeks turned pale pink. “Sometimes I’ve been around when Harry’s having his visions of Voldemort – it’s the same thing to talk him out of those, only he’s spasming with the Cruciatus curse and it’s much harder to bring him out of it.”

Snape looked down at his own hands, his long fingers wrapped around the cool teacup. “I think, Miss Granger, that perhaps you should join Mr. Potter in his Occlumency lessons. You might have enough skill to talk him through those as well. We will meet in my office, Mondays after dinner – not this week, as he is incapacitated, but next week.”

Pomfrey bustled about the infirmary, administering vaccinations to the remaining sixth year students. Her voice was bright and cheerful – she had taken a calming potion to recover from the earlier stress – and she filled syringes, gave vaccinations, and answered the students’ questions with efficiency. Before returning to the task of vaccinations, she had set up a privacy screen around Potter’s bed and it blocked the sunlight from the boy’s pale face. Snape sat in the shadows by the bed.

When Dumbledore had waltzed in, proferring lemon drops and tea and grandfatherly wisdom, Snape informed him that he was monitoring the Potter boy, ensuring that Dumbledore’s favorite Gryffindor came to no further harm. He was disagreeable, unpleasant, his usual sarcastic self.

When Dumbledore and Pomfrey were gone, when the infirmary was empty of students, Snape reached out and brushed Potter’s unruly hair off of his face. His fingers hesitated on the boy’s forehead, still clammy from the ordeal. “I’m sorry,” he whispered to the sleeping boy - the image of his father and yet so unlike his father. “I’m sorry, Harry.”