Hope You Have Sweet Dreams Tonight

"Voldemort's mind magic was extremely powerful—almost impossible to break." Wizet shook his head and continued probing with his wand. "And she's too old, too frail..."

"Indeed..." Dumbledore agreed with Wizet's assessment, seeming to realize what Wizet intended to do.

"So you intend to... alter that false memory and let a new memory overwrite it?"

"A cold lie had wrapped Hokey up for so many years..." Wizet looked toward the carefully tended little garden. "Like this garden, she should be able to enjoy the sunlight."

Altering memories was not as simple as it seemed. It often required incorporating the surrounding setting—when falsehood became truth, truth also became falsehood; where there was nothing, there could become something.

By Wizet's estimation, Voldemort had likely used a similar approach when he altered the memory in the first place;

Voldemort had visited late at night and, exploiting Hepzibah Smith's trust in him, taken House-elf Hokey's place to serve Hepzibah Smith a cup of lethally poisoned nightcap;

A House-elf preparing a nightcap for her mistress every evening was simply habitual. Thus, he could use that fact to confuse and alter Hokey's memories, making her believe that she had done it herself.

There were two key points. The first was the starting point for altering the memory: the night Hepzibah Smith died. They had to begin with that night;

The second was something Hokey had diligently kept doing: the little garden surrounding the house, which she had always carefully tended and protected, keeping its plants full of life.

"Yes! She deserves to enjoy the sunlight." Dumbledore sighed. "But it won't be that easy, will it? Voldemort had deep knowledge of mind magic—and of the soul."

Having been enemies for so many years, Dumbledore naturally knew Voldemort inside and out. He was, in the truest sense, someone who