"Are you alone?" She swept past him without waiting for an answer. The chair in front of his desk was immediately singled out and sat on, and her green eyes arrested his. "Sit down."
He did.
"My name is unimportant, Professor. All that you need to know is that I am a Muggle, and that I will change this world."
Speechless, he gazed at her in sullen silence.
Her green eyes remained unchanged, still merely truthful and clear. "I killed the thing that would have killed you, tonight. In seven years its virulent poisons would have coursed through your body, shutting down organ after organ. I have changed that."
"What are you doing here?"
"Changing what was. I just said that." She closed her eyes and exhaled through her nose. "Think about this, Professor: everything that ever happened and ever will happen is happening at this moment, at the exact same time. You are being born. Your parents are meeting for the first time. You are dying as the poison destroys you from the inside out. You are meeting Lily for the first time. You are falling in love with her. You are learning she is dead. Do you see?"
He refused to speak, watching her with a furious look.
"Alright, think of it this way. Whatever is happening now is a culmination of everything that happened before and the precursor to everything that will occur afterwards in this timestream. It is all happening at the same time, albeit in separate timestreams. Now, by the addition of myself, I have altered this timestream and all the others, because they occur in unison. I am the only human being alive who has no past or future here."
Regardless of her origins, her voice and eyes held his attention with ruthless calm. He shifted in his seat as she bored inside him, laying bare all of his inner workings, the churning of his mind and the pulse of his body. "You said you killed what would kill me."
She nodded once, a partial inclining of her head. "Nagini would have sunk his fangs into you seven years from now and you would have died. Early this evening I caught him in the catacombs and cut off his head."
Snape sat back in his chair, black eyes widening by a margin slightly less than the width of a human hair. "You killed the Slytherin serpent."
"Decapitated him, to be precise, but yes."
"How do you know it would have killed me?"
Her neatly clasped hands, at odds with her casual clothes, settled on her knees. "I know everything that has happened or will happen here. It's why I'm here. I saw the snake killing you, as clearly as I see you now."
He couldn't help but sneer. This was ridiculous. "So you're saying you're some kind of omniscient god?"
"No. Just a Muggle trying to find her way." Her green eyes were still fixed on his black ones with tangible force, despite the tranquil knowing that swum in the recesses of her gaze. She knew all of this, just as he knew she was going to be an integral part of the future, the one thing that could possibly divert destiny. "I've changed this time," she said suddenly, startling him. "By the simple addition of myself, I have altered this world completely and irrevocably. From now on, nothing will be the way it was—nothing will happen as it had happened, and no one will be exactly who they were and would be."
"You're insane. How did you get in here?"
For the first time an edge of exasperation made her look at him sharply. "Think whatever you like, you stupid man. You won't remember much of this anyway."
As if on cue, the corners of his vision went fuzzy, drawing inward like a dark curtain until everything was gone, drowning in anaerobic silence.