"Stay here, Potter," Snape ordered imperiously, and made his way across to the Alium, clearing a path as he did so with a flick of his wand. The man looked remarkably similar to the one he saw in the mirror each morning, unlike the two versions of Potter, which were markedly different. As he came to a rest in front of the window, he cast a muffiliato, while watching his counterpart do the same.

"Well?" he demanded, as soon as the faint humming told him that the muffling charm was active. "What information do you have for me?"

His counterpart didn't respond at first, instead taking a moment to assess him carefully. "I noticed your reaction to my mentioning the curse on the ring horcrux," he began, after a moment. "Has the headmaster become cursed in your world, as well?"

Snape said nothing, but his alter-ego's lips formed a thin line as he watched Snape for a reaction. "I am sorry to learn it," he commented, in response to Snape's silence. "We are experiencing the same misfortune. I imagine the problem this poses is somewhat exacerbated by your role as a spy."

Snape simply stared, with an air of boredom, as if waiting to hear something of use. He had no intention of confiding any information at all in his Alium self, and the man in front of him seemed to know it, as he did not wait for a response before continuing.

"Of course, knowing the man as I do, I imagine he plans to use his impending demise to advance the war effort. He will wish you to be given control of Hogwarts, I daresay. And, to that end…"

Snape leant against the table behind him in a show of casual disinterest at his other self's musings. The man was rather fond of the sound of his own voice, Snape noted with derision.

His alternate self narrowed his eyes suddenly, seeming to have come to a conclusion. "If you need to seal the Dark Lord's trust in you…. perhaps Albus intends to have you kill him to cement your position?"

In response, Snape merely stared impassively at his alternate self, which the other man apparently took to be a full confession.

"An effective leader, Dumbledore," the Alium-Snape said, shaking his head, "yet capable of such cruelty. I imagine he has instructed you not to confide this information in anyone else. However, I'd like you to inform Harry before any action needs to be taken."

"Potter?" sneered Snape, his voice dripping with derision, "Why, so he can have the information ripped from his imbecilic mind by the Dark Lord? Why should he know?"

"Because," came the answer, "He needs an adult on his side that he can trust and that trusts him."

Snape snorted impatiently and turned to leave, having wasted quite enough time on this nonsense. Perhaps he could find a way out before Weasley burst his way through the wards.

"Stop!" he heard his own voice command, and he halted, cursing his own curiosity even as he did so. "I would not speak to you if I did not think it important."

At this, Snape turned, raising an eyebrow in challenge.

Seeing he had the man's attention, Alium-Snape continued. "You must hear me out- let me explain why you should tell him."

Snape met the man's eyes in a blank challenge and willed his counterpart to simply get on with it.

Taking a deep breath, the man continued, at a calm and unhurried pace. "I have raised Harry for most of the last five years," he said, with a significant glance at Snape, "and I can tell you that he does far less in the way of foolish Gryffindoresque plots when he's given all the relevant information in the first place."

This gave Snape pause. "You say you have raised the boy?" It was a mark of how surprising this revelation was that Snape requested the confirmation; he was not in the habit of pointless repetition in conversation.

"Certainly," confirmed his counterpart, with a nod. "He has been my ward since towards the end of his first year. I have spent every summer, aside from the first two weeks, with him since that time. And every holiday break, in addition to Thursday evenings during term time," his lips quirked up fondly at the recollection, and Snape found himself seriously doubting whether this was the Alium at all, so unlike himself was the man before him. Then, it got worse.

"I consider him to be my son," his Alium-self continued, speaking firmly, and Snape felt positively nauseated at the thought. He opened his mouth to ask the man whether he'd lost his bloody mind; taking in a virtual clone of Potter, of all people, but his alternate self raised a hand, as if to stem the tide of the vitriol Snape wished to direct his way.

"I know what you think of him," the man in the Alium said, a note of steel in his voice further compelling Snape to keep his silence, "and why you think that, but the boy is not arrogant, Severus. He has been a victim of Petunia Evans and her oaf of a husband and son since he was too young to form memories. I recognised the signs because he was one of my snakes, and I was able to act upon them because he was under my jurisdiction. He was abused. As your version of him still is, when he goes home."

A moment of silence followed this pronouncement as Snape briefly considered, and then disregarded, the possibility.

"Ridiculous," he sneered, shaking his head dismissively. "The brat is worshipped and adored by his relatives. You have no idea of the breathtaking extent of his arrogance and sense of entitlement. Perhaps your version of Potter may be a victim of abuse, but the one I have had the misfortune to share my reality with could not be farther from it."

The man in the Alium raised an eyebrow, staring incredulously at his counterpart. "You are either confunded or being intentionally blind, Severus. Look at the boy!"

Snape rolled his eyes. "I have seen him."

The Alium-Snape's eyes darkened still further. "It seems to me," he hissed, "that no adult in your entire accursed universe has truly seen that child since Lily died!" He pinched the bridge of his nose, inhaling deliberately.

"Just… look." With this, the man deliberately locked eyes with Snape, a question in his gaze. Snape recognised the invitation, and nodded. Immediately, his mind was confronted with a conversation from earlier today. He recognised the Harry Potter he had taught for five years, perched on the edge of the desk currently behind Snape, muttering softly.

"Someone should have taken me from there." He said, quietly, eyes on his shoes. "They know how I'm treated. They know.." he paused for a moment to gather himself, continuing in an almost-whisper, "My Hogwarts letter was addressed to the cupboard under the stairs… the Weasleys had to pull iron bars off my windows, and I know they told Mrs Weasley about them. They always send me food for my birthday because they know I don't get enough... In third year, I blew up my aunt and ran away from home. I asked Dumbledore not to send me home for the summer too, back in first year." He took a breath, slightly unevenly. "No one ever did anything. Someone… someone should have done something."

Snape shook his head to clear the image. "Potter may have fooled you with his little sob story," he scoffed, "but such tactics will not work on me." He straightened, staring derisively at the man before him. "You've gone soft, Snape, since the Dark Lord's defeat."

The man in the Alium let out a snort, nodding as he did so. "I'll agree with you there," he said wryly. " Or at least, I've gone soft, as you put it, since I became Harry's guardian. But I can't say I believe it to be an altogether terrible thing."

"Oh really?" asked Snape sardonically. "How very nice for you."

Silence reigned once for a moment, before the Alium-Snape spoke up again. "If you can trust no one else, Severus, trust yourself," implored the other man, quietly.

"Analyse your own memories of the boy, but look for an abused child, rather than a spoilt Potter brat. You know the signs. He is not arrogant, believe me. And he needs your help with occlumency, especially now he knows about the horcruxes."

"I will never again teach that boy occlumency!" snarled Snape, relieved to be on more familiar footing in the conversation. "The brat deliberately went into my pensieve!"

"And that is inexcusable," interjected his counterpart, calmly, "but so is a master of mind arts using a pensieve to protect his own privacy, without offering the same courtesy to the untrained fifteen year old he is teaching. You'd been in his pensieve since the first lesson."

To this, Snape could say nothing in his own defence.

"Harry is talented at mind-magics, Severus," offered his alter-self. "All that is needed is trust between student and teacher, and the correct approach. I have told him what worked for his Slytherin counterpart. I have also," he continued, unapologetically, "helped you to gain his trust, by telling him about the vow, and about your part in the prophecy."

Snape felt the colour drain from his face. "You had no right!" he hissed, livid.

"I did what was necessary," snarled his counterpart, equally wrathful in his response, "I refuse to see a version of my child adrift in a sea of grief and misplaced guilt without a single reliable adult or the capacity to defend his own mind!"

"I cannot be a 'reliable adult' for Potter!" sneered Snape, vehemently. "It is an idiotic idea. I am a spy for the Dark Lord- being around me is dangerous for us both. Quite apart from that, we despise each other!"

The man in the Alium took a step forwards, nostrils flaring as he spoke, "You made a vow, Severus! You are well placed to help the boy, and you will be able to tell him about Dumbledore once he's mastered occlumency." The man raised his hand, cutting off any protest Snape might have made. He resumed his speech once more, after a moment, both men breathing ever so slightly heavier than they had been, his voice lower and more calm.

"I see we are not likely to reach an accord," the man said, a note of resignation in his tone. "Now, as time draws short, legilimency seems to me the best way to share with you my research into horcruxes, if you would wish to?"

Against his better judgement, Severus met the other man's eyes and plunged into his mind, gathering information as it was offered to him. A spell to identify horcruxes, ancient tomes, the titles of books that may be useful, memories of destroying horcruxes, experiments on transferring them- Severus stored it all.

Finally, after what seemed like hours but spanned only a few moments, the information was exhausted. Severus was ready to pull back, but found his alternate self offering up other, unrelated memories. He hesitantly accepted them, and felt himself immediately drawn in, fully and inextricably immersed with a strength to which he was as wholly unaccustomed.

He was sitting in the Great Hall, his carefully-laid plans crashing around his ears as his newest snake stumbled off the stool into the silence, looking incredibly frightened and impossibly small. Seated in his office, he was frowning at a medical report, requisitioned for one H. J. Potter, the words malnutrition and restricted growth staring out at him from the page. He was flicking through the record of letters sent to Hogwarts first years- Harry Potter, Cupboard Under the Stairs, 4 Privet Drive, Little Whinging, Surrey. He was in Dumbledore's office, arguing vociferously, "He can go back for two weeks to renew the wards, Albus, but I will be monitoring him and he'll not be left there a second longer than necessary!" He was sitting on the bed beside Potter in his own spare room in Spinner's End, waiting for the clock to switch to midnight on the 31st of July. Heart pounding, he was running across his Hogwarts quarters to a room he'd never seen before, which contained a whimpering Potter, crying out in his sleep- "Please let me out, Aunt Petunia! Please!" Beside his own simmering cauldron, he observed as Potter carefully added powdered bicorn horn to a silver solution, saw the boy's eyes light up as it turned a brilliant blue. An older Potter cast his patronus for the first time. "A doe!" Potter exclaimed, delightedly.

Suddenly, the memories stopped and he found himself staring once more into his alternate self's obsidian orbs.

"Promise me that you will look after that boy, Severus. Promise on Lily's memory. " His alternate self's voice was quiet, barely a whisper, but imbued with significance, his tone the one he reserved for the most serious declarations, the most menacing threats. "He deserves more than mere survival."

Snape, his mouth dry, mind still whirling, simply nodded. A moment later, he blinked in surprise at the agreement he had just made, but the man in the Alium smiled at him, satisfied. The promise had been made. On Lily's memory. And Snape knew he would attempt to keep it.