Disclaimer: It goes without saying of course, but I do not claim to own any of the Harry Potter characters or their magical universe created by J.K. Rowling. I'm writing this story purely for fun and not for profit.

A/N: This story owes some of its inspiration to the work of these other authors:

"Why Not" and "No Matter the Cost" by NorthAngel27, "A Valentine's Quartett" by the Snapettes (Occlumency)

Especially the first two, in my mind, have become almost part of canon, and I would be unable to write Snape / Sinistra without that influencing me. They are great stories and I recommend you do check them out.

A Paradox at Dawn

The early morning sun rising over Hogwarts illuminated a scene of destruction and chaos. The grounds were strewn with the lifeless bodies of different creatures, and the castle itself had suffered badly. The Astronomy Tower, however, was still standing, casting its mighty shadow over the courtyard below. High up on its viewing platform, a small female figure could be seen, leaning over the railing, while the morning breeze tore at her robes and long hair.

Professor Aurora Sinistra leaned into the wind and closed her eyes. Her stomach tried to tell her that she should be at the feast, along with everybody else, but she needed to be alone, and was as oblivious to its rumbling as she was to the dark rings under her eyes, and the ache in her back and legs. Like everybody else she bore the signs of a night without sleep, a night of fighting, of fear, of tears, followed by a victory they had hardly been able to hope for.

Victory. You-Know-who was no more. The horrors of the past year, when the Death Eaters had ruled the school, were all over. And yet, to her, it felt not like the beginning, but the end of all hope. The brightest star in her life had fallen. The emptiness inside her was as overpowering as a mighty black hole, sucking up all happiness, and clumping it into a mass of infinite heaviness.

She let go of her tears, which flooded from her eyes in hot streams, but offered no consolation, no comfort, no release. She had known all along that Severus was on their side. She knew him better than any of her colleagues, of course, but, nevertheless, she was disappointed by how readily they had all believed in his apparent betrayal. Unlike her, they failed to see how he was actually protecting them from the worst. As a true Ravenclaw, however, she was wiser than to show her loyalty and support of him openly. Nothing could have been more dangerous to him. He was walking a thin line as it was, keeping up the appearance of a loyal Death Eater, running the school in his Dark Lord's best interest, while preventing the worst acts of cruelty towards the students. The best she could do was not to cause him any extra trouble, which was far more than could be said of the rest of the faculty, who made no attempt to hide their loathing and disapproval of his leadership. 'You always insisted that you would have to go it alone. You never relied on anybody, and you were right,' she thought.

She wiped away her tears with the sleeve of her midnight blue robes, and let out a big sob. She had spent some of the happiest moments of her life up here on the Astronomy Tower, and they had not been due to her love of stargazing. As she ran her hand over the cool stone making up the wall next to her, images of the dark young Potions Master backing her against that very wall flooded her mind, images of him kissing her passionately, while his graceful hands roamed over her body, and his intense black eyes burned holes into her. Now all she had left of him were memories, but in those memories, he would always live on.

For several years, they had shared a secret affair, and the sex had been very good indeed. But while her feelings for him had grown into much more over time, to him, it seemed, it had never been more than an arrangement of convenience. The year when You-Know-Who returned, he had broken it off, without even saying a word to the effect, but leaving her in no doubt that it was over. And while he reverted to treating her with the same cool formality as all his other colleagues, she had been pining away for him. Her heart had fluttered every time he swept past her in the corridors, every time she heard his deep, resonant voice in a faculty meeting, every time their eyes briefly met when they passed each other in the library. In fact, she had spent unnecessary amounts of time in the library, waiting for the odd chance to be alone with him. And all those years, she had never given up hope that, one day, once those dark times were over, they could be together again. Now the day had arrived, but her hopes were shattered.

Slowly, she descended the stairs leading down from the tower, and wandered through the castle's corridors, aimlessly. But when she suddenly found herself in front of the headmaster's office, she realised she had wanted to come here all along. The gargoyle was lying toppled over on the floor. It just gave a faint moan when she stepped over it, and climbed up the spiralling staircase. The door to the office stood half-way open. Hesitantly, and with the sense of a child doing something forbidden, she entered.

She had not been inside this room since Dumbledore's death. Severus had guarded the place like a personal sanctuary. Even faculty meetings had been held in the staff room, and, as far as she was aware, none of the teachers had set foot in here during his term of office. Had he been worried that an indiscretion from one of the portraits might give him away? But now, it seemed that access was free for all.

Taking a look around, she noted how little had changed since the time that Dumbledore had resided there. On a table in the corner, the same curious silver instruments still whirred and puffed quietly, Fawkes' perch still stood behind the desk, even though the phoenix had long left Hogwarts, and Dumbledore's heavy stone Pensieve rested on a sideboard beneath the window. It appeared as if Severus had left everything exactly as it was. 'You never felt like you belonged here, did you? To you, it always continued to be Dumbledore's office,' she mused.

There was little that would have told you that a Potions Master had occupied the office lately, none of the jars and bottles containing slimy substances, or pickled plants and animals, that had once adorned the walls in Severus' dungeon office. Except perhaps for the fact that Dumbledore's display cabinet, which he'd used to store collected memories in his time, now held a collection of potions bottles. She peered through the glass pane to read the labels, written in Severus' edgy, crowded script: "Dreamless Sleep", "Strengthening Draught", "Essence of Dittany", "Felix Felicis", "Blood Repleneshing Potion", "Mind Sharpening Potion", "Veritas Serum"....

'Of course, he would have kept a stock of all the essentials,' she thought. Self-sufficiency would have been of essence for him during the past year. If only he had taken some of that Felix Felicis potion the night before, perhaps he would still be alive. There was also a tiny vial, containing a clear liquid, whose label did not bear the same handwriting as the others, but instead had the words "Phoenix Tears" emblazoned upon it in big sweeping lines. She wondered whether it was Dumbledore's hand.

The only other addition to the room was the large portrait right behind the throne-like chair. The engraved gold plaque at the bottom of the frame identified it as Dumbledore's. The occupant, however, was absent, as were all the other headmasters and headmistresses of times long past. Apparently, they, too, had gone to the Great Hall, where the feast was.

She bent over the intricately carved desk beneath the portrait, and took a look at the heavy, leather bound book that lay open upon it. It appeared very, very old, and was written in a dialect of Runes that she could not decipher. What had Severus been reading about so close to his death? She brushed across the pages with her fingertips, almost tenderly, as if she could somehow connect to him by touching the parchment where his hand had rested so recently. A black eagle quill was lying on the desk beside the book. She took it, and lovingly ran the soft plumes across her palm. She would keep this as a token to remind her of the beautiful hands that had used it. Closing her eyes, she pressed it against her chest, remembering how those hands had once cupped and gently squeezed her breasts, while his lips breathed hot kisses behind her ear and his arousal pressed into the small of her back...

She was suddenly pulled out of her reverie by a familiar voice, addressing her from behind.

"Ah, Aurora, reminiscing about the past?"

She spun around, slightly embarrassed, and hoping her facial expression had not given away the nature of her thoughts. Dumbledore had returned to his portrait, and was smiling at her benevolently.

And then, it struck her. Shouldn't there be a portrait of Severus? According to Minerva, Dumbledore's portrait had magically appeared within less than an hour of his death. And ancient tradition had it that everyone who ever had held the post of headmaster, no matter for how short a time, would be preserved to posterity in the same fashion. Could Hogwarts really be so ungrateful, to not grant Severus this one last honour? Feelings of outrage and indignation erupted in her heart at the thought of this disregard for the man who had given his life to their cause.

"Albus, why does Severus not have a portrait like you do?" she asked, bitterly.

"Because someone saved him, I suppose," the old wizard explained calmly, "and I'm glad to see that it was you, Aurora."

Whatever answer she had expected, this was not even remotely close. Dumbstruck, it took her several seconds to process the information.

"Unfortunately, I think you're wrong, Albus. I don't even recall seeing him last night," she responded wearily, and still somewhat confused. "And I don't think I was under the Imperius curse either."

"Ah, that's because you haven't done it yet," Dumbledore replied, with his blue eyes displaying their trademark twinkle.

Unlike most other people, Aurora had never had any difficulty following Dumbledore's often mysterious statements. He rarely spelled things out for you, a habit she suspected had been acquired from years of teaching. But as a Ravenclaw, she had to be good at solving riddles, or she would not even be able to get into her common room. And so it took her only moments to understand what he meant.

The only possible answer, of course, was time travel. As the school's Astronomy teacher, the mysteries of space and time fell into her remit, and she had always devoted a lesson to the subject in her OWLS class. She could almost hear her own voice in her head, as she lectured to a crowd of mildly interested students.

'Time travel is dangerous, as it creates havoc in the space-time continuum in ways that could easily drive yourself and others insane. Imagine if you suddenly found yourself opposite your doppelganger from the future! It is therefore essential that time travellers remain unobserved. You also have to be extremely careful with your actions, as you could easily change the course of the future in unpredictable and undesirable ways. Even with the greatest precaution, any change you bring about leads to the creation of paradoxical phenomena. You will find things that are incompatible with your understanding of the world, and you won't be able to explain them until later, when you have actually undertaken the journey. It is for this reason that time travel has always been strictly regulated by the Ministry. For instance, you were never allowed to go back by more than one day. And lately, the authorities have decided that the risks outweigh the benefits, and that it is best to stop the practice altogether...'

So was this one of said paradoxes? Was there no portrait, because, in the future, she would go back to change the past? Was there no portrait, because Severus was actually alive? But to move back along the axis of time, you needed a Time Turner, and the Ministry had destroyed them all. Or had they?

"Albus, don't tell me you keep an unauthorised Time Turner hidden somewhere?" she asked.

"Ah, hidden is not the right word," the old headmaster said, barely able to suppress a grin. "But I did feel it was prudent to keep one at hand. Often times you will find that the best way to conceal something, is to keep it in plain view."

Then it dawned on her. She approached the little table in the corner, where Dumbledore's collection of weird and wonderful instruments continued to buzz and oscillate innocently, and sure enough, sitting inconspicuously in their middle, was an elaborately engraved silver Time Turner. She was not at all surprised that the old headmaster's little secret had gone unnoticed. Few people ever gave Dumbledore's contraptions a second look, assuming them to be pointless fancies of an eccentric old man, whose sanity had been questioned by many.

With a sense of awe, she reached out to remove the precious instrument from amongst the other curios on the table, and placed the chain around her neck. Now she just had to figure out a means of helping Severus in a way that would not jeopardise any of the events of the past hours.

"Albus, would phoenix tears be able to cure the sort of injuries that Severus sustained?"

"Indeed they would," the shrewd old wizard confirmed, his face beaming.

Aurora walked up to the cabinet in the corner, and took the little vial from its shelf, placing it into a pocket of her robes along with the bottles of Blood Replenishing Potion, Strengthening Draught, and Felix Felicis. Before she could slip out of the room, Dumbledore's painting called after her.

'Aurora, I don't need to remind you to be careful, do I?'

'Don't worry, Albus, I know what I'm doing.'

The sound of merry chatter and clinking goblets could still be heard through the doors of the Great Hall, as she walked past them on her way down towards the Shrieking Shack, and she felt confident that her absence would not be noticed.

A/N: Please review. This could stand as a one-shot, but I might continue...