Disclaimer: The sad truth is that I am not J.K Rowling, therefore, I do not own Harry Potter or anything here that you may recognise.

One Great Favor:

"Lightening Struck Tower" from the perspective of Severus Snape

Storm clouds coiled overhead, steely grey and amethyst swirling in their depths. The wind grew from a sultry breeze to a freezing gale, subtly, though in a short space of time, and now accompanied by a mist of rainwater. It was as though some higher power could sense the events that were to happen tonight, and so arranged the atmosphere accordingly, to complement, or to further, the eerie mood.

Severus Snape paced his office, barely noticing the swift change in the weather, his hands clenching and unclenching. A deep frown was carved into his face as he attempted to overthrow the thoughts and emotions that were currently contaminating his mind; however, as good an Occlumens as he undoubtedly was, he found that he simply could not. Hatred, anger and guilt ran through his veins, more prominent than blood, making his heart beat furiously against his chest.

Noises came from above, harried voices and frantic footsteps...Severus froze on the spot; it was happening. He needed to go, he needed to go right now, but his body would not comply.

The door suddenly burst open to reveal the diminutive silhouette of his colleague, Filius Flitwick, forcing Severus out of his stupor. Flitwick's glasses were askew and his chest was rising and falling rapidly as he panted for breath, leaning against the doorframe for support.

"Death-Eaters – everywhere...so many of them...and Dumbledore's away! We just can't hold them back...we need you Severus...too many..." the little man wheezed, and then jumped into the classroom as a crash resounded from above.

Severus stealthily drew his wand from his cloak and held it aloft, as though in preparation for the battle, but quickly directed it at Flitwick and muttered "stupefy", causing the Charms professor to slump onto the floor.

Severus hesitated for a moment – but only a moment – and then in two swift steps was out of the door. He almost hurtled into two small figures that were just outside of his room; from the glow of their lit wands, he could see that it was Granger and the dotty Lovegood girl. Severus didn't stop to think about why two of Potter's friends were stationed outside of his room - that wasn't hard to guess at - but instead thought fast at how to overcome this slight hindrance.

"Professor Flitwick has collapsed; I must go and join the battle, you are to remain with him in my office and tend to him," Severus hastily instructed them, not stopping to watch them disappear into the room. That way, they would be kept out of the ensuing battle, and out of harm.

As Severus glided swiftly up the stairs and out of the dungeons, the noises from the battle grew louder, until he was in the midst of it. People were being knocked backwards, faces were contorted with anger, and there were blinding flashes of light as curses were being cast through the air; but Severus passed through the battle with relative ease; it was a simple matter of dodging, as none of these curses were being directed at him due to the convenient fact that both opposing sides believed him to be on their side - for now, he thought wryly. He thought he heard someone call out to him, though he couldn't be sure who it was, or what side they were on; nevertheless, he could not stop.

Severus Snape flew up the main staircase, his black cape billowing behind him. He did not stop once to catch his breath; he did not have any time to spare. As Severus moved higher into the castle, the battle noises faded into the background.

It seemed like a lifetime as Severus wound his way through the long corridors...dark, deserted and empty...much like how he felt inside. A strangle grumbling sound echoed through the corridor; Severus almost jumped in fright, but kept running. At first he had thought it was thunder, but after the thunder did not cease, he realized it was a low rumble of voices.

But he was alone...he looked over his shoulder to confirm that there was no one behind him. The corridor was definitely deserted. Severus listened more closely to the voices...some spoke in quiet tones and others harshly, but he could not make out what they were saying; they all spoke over the top of one another. They sounded oddly familiar. Severus's footsteps did not falter, or even slow, yet the voices did not fade – it was as though they followed him.

It was beginning to give Severus a headache when, with a jolt of surprised, he recognized the voices; they all belonged to Dumbledore. They overlapped each other; layers and layers of Dumbledore's deep voice, speaking different things. Severus concentrated and soon untangled the voices, so that he could distinguish each sentence.

"What request could a Death-Eater make of me?"

Severus almost stumbled upon hearing this; Dumbledore had asked him this very question before...sixteen years ago, to be precise. Severus then realized that these voices were not emanating from the stone walls of the corridor at all – they were inside his own head. The words were as a clear as when they had been spoken, when Severus had begged Dumbledore to protect her -

"You disgust me; you do not care then, about the deaths of her husband and child? They can die, as long as you have what you want?"

Severus flinched at the revulsion in Dumbledore's voice, just as he had the day those words were first spoken. More of Dumbledore's words ricocheted through his mind...these were spoken the night Lily Potter died.

"Her boy survives. He has her eyes, precisely her eyes. You remember the shape and colour of Lily Evans's eyes, I'm sure?"

Lily gently brushed a lock of red hair out of bright, green eyes...they had always reminded Severus of emeralds...precious and rare...no! He blocked the painfully beautiful image from his mind. He could not afford to think about Lily...not now...what would she think about what he was about to do? Dumbledore's voice pierced into his mind again.

"If you loved Lily Evans, if you truly loved her, than your way forward is clear. You know how and why she died; make sure it was not in vain. Help me protect Lily's son."

Which is what he had done, isn't it? Which is what he is still doing? Which is why he is about to commit this wretched act...

Once again, Dumbledore's voice echoed in his mind.

"My word, Severus, that I shall never reveal the best of you?" The bodiless voice sighed, "If you insist."

Severus recalled the time when he had made Dumbledore vow never to reveal his love for Lily Potter; never to reveal that he was protecting Potter's son. Dumbledore had been true to his word, like he always was.

"You know, I sometimes think we sort too soon,"

Severus was not entirely sure why these words had affected him so much, but they had; he scowled, but felt something stir inside of him as the words were spoken afresh. Dumbledore had been implying that Severus possessed bravery worthy of a Gryffindor...

"You have done very well, Severus. How long do you think I have?"

Severus recoiled at this memory, more recent than the others...he had been unable to save Dumbledore from the curse that threatened claim his life. Yet the old fool went on to thank him.

"I am fortunate, extremely fortunate, that I have you Severus,"

Despite the coldness in his heart, Severus felt a pang of warmth. He barely registered his surroundings as his legs continued to carry him further up into the castle.

"Voldemort believes the school will soon be in his grasp. Yes...and if it does fall into his grasp, I have your word that you will do all in your power to protect the students of Hogwarts?"

Yes, Severus had given him his word. The time to put his promise into practice was fast approaching. More words resonated through his mind.

"You alone will know whether it will harm your soul, to help an old man avoid pain and humiliation. I ask this one great favor of you Severus..."

Severus scowled, and felt a rush of anger. The one great favor he was about to perform – the only favor that he had ever attempted to refuse. Dumbledore had asked too much of him this time, the old man had gone too far...

Severus Snape came to a sudden halt as he heard other voices – voices coming from just above him.

"I said no!" Severus recognized the shout as Yaxley's. There was a flash of light and something heavy thudded onto the platform under which Severus now stood. He was standing at the foot of the winding staircase that led to the Astronomy Tower – he had reached his destination. He just needed to walk up those steps...cold horror flashed through him...how could Dumbledore expect him to do this?

"You gave me your word, Severus,"

The final discernable echo of Dumbledore's voice wrung through his brain and into his every being, making him sweep up the rickety stairs. The voices grew louder in his mind, to the point where he could not distinguish what they were saying.

"Draco, do it, or stand aside so one of us –"

Alecto Carrow's screech was cut short as Severus burst through the door and onto the landing of the tower. His eyes swept the scene before him; there were four Death-Eaters spread out in the space, their greedy eyes fixed on the two figures in front of them. Draco had his wand pointed feebly towards Dumbledore, who was slumped against the wall, wandless, and looking weaker than Severus had ever seen him. His pale blue eyes, however, showed no fear of what was to come.

"We've got a problem, Snape," said Amycus Carrow, whose wand was fixed on Dumbledore, "the boy doesn't seem able –"

"Severus..."

Severus froze; this one word, though spoken quite softly, sliced through the echoes in his mind – it was spoken by the Dumbledore in front of him. He met Dumbledore's eyes and walked forward, pushing the boy out of the way.

"Please, Severus," Albus Dumbledore begged, his piercing blue eyes reaching deep into Severus Snape's black ones. The echoes in his mind rose to mind-numbing hum. Severus, for a fraction of a second, hesitated; he felt the deepest disgust, the deepest revulsion at what he was about to do. Yet, somehow, he raised his wand; he had to do this, he knew that it was his duty - like every other damned thing.

"Avada Kedavra!"

Severus Snape did not see the green flash of light, nor did he hear the Death Eaters cruel laughter; he saw only Dumbledore, falling, the twinkle in his eye forever extinguished. And for that short space in time, Severus Snape loathed the man, loathed him with all his essence; how dare he make him do that! How dare he!

Severus Snape loathed himself, too. It was all he could do not to throw himself over the tower right after Dumbledore - death seemed like a welcoming prospect just then. But he exerted every ounce of his self-control to push down the anger, the hate, the hurt, the bitterness, until his face was - once more – an inscrutable mask...until all he could feel was... nothing. Severus Snape felt nothing. He had just killed the only person who had ever truly trusted him.

The echoes of Dumbledore's voice had died away, leaving a terrible emptiness in Severus' mind, though not before leaving one last message.

"Thank you, Severus,"

And Severus Snape knew that he would never hear Albus Dumbledore's voice again.

A/N: Accio reviews! ~ I hope I did Severus Snape justice, what say you?