"Why did you come to me for help?" Tom asked one rainy evening. The pattering on the window and the lit candles almost made the scene intimate.
"If it could have been avoided, I would have never seen you again. Initially I thought I had just been teleported into your shop by some sort of portkey magic, or something similar enough. I'm not the most skilled liar, but I'd never seen you in the shop before so I felt my on the fly excuse would be good enough ." She closed her book on her finger and gave him her full attention. "As soon as I saw the date though, things started to fall into place."
He waited for her to go on, she was in an uncommonly accommodating mood.
"So I was never going to have to see you again, you wouldn't remember me, I didn't mess up the time line. All was well. Except it wasn't. Every time I went out to fetch a book I would find myself outside your shop. When I needed more brewing supplies, or a chart, there I was again about to open the door of Borgin and Burkes. It was maddening, and eventually I started to work out that it was the necklace, you had to have one."
"So the pendants are drawn to each other?" He thought for a moment and added,"It doesn't make sense. When more than one of a singular thing exists at the same time it creates a paradox. Shouldn't they be repelled from one another? Avoid some sort of cosmic meltdown ?"
"I thought so at first, but these are different. They aren't normal, and they don't follow our understanding of time. So that's when I thought if I got them close enough, they would reverse the power that brought me here."
He remembered the scene she had made, and her obvious frustration.
"When that didn't work it had to mean something else. You were the only person in that store and so the most likely variable. I don't know how you're involved, but you were meant to be a part of this."
That night Tom slept poorly, even though had kept to one cup of coffee and had left at a reasonable hour. He had a sinking feeling in his stomach that he couldn't place the reason for, and it made him toss and turn. He dreamt of Hermione. She was sullen, her usual fire gone, and she mumbled things that turned to garbled nonsense in his ears.
He would remember none of it.
She was a better liar than she let on. Her calculations were complete and she knew exactly what she needed from Tom, and she had got it.
When he woke she was gone, but he did not miss her because he did not remember her. Not at first.
It had been her plan all along to slip away, and she would have done so if Tom had been a lesser wizard.
For a while he had suspected Hermione to be altering his memories, the headaches were his first clue. He had never had a headache in his life, and to suddenly start was too much of a coincidence, and he put together that eventually, when she did leave, all his memories would be gone with her.
Not willing to let it all slip away, he started collecting them every night. He let her take what she would, so on the day she would leave, he would know and remember. To make sure he found them he tucked them safely away in his diary.