When Harry materialized on the field, holding Cedric's limp body, claiming He had returned, Hermione was almost able to dismiss it as temporary insanity. When Harry was dragged away by Professor Moody, she could almost convince herself it was because Harry obviously needed help and once he was no longer Confunded, everything would be fine. When Cedric was not immediately revived, her doubts became a bit more nagging. A field injury, probably. Anything in that maze could have injured him.
When the Diggorys quickly become inconsolable, Hermione acknowledged the possibility of Cedric's death. This whole tournament was outlawed because of student deaths. It could have been anything. Who knows what was in that maze. But when Dumbledore looked for Harry and couldn't find him, when he visible paled for a moment before disappearing in a flash of Phoenix fire, she knew. And while Hermione had imagined this day, dreaded this day, ignored the very possibility of this day in her mind countless times, she had always pictured herself rising to the challenge, confronting the unknown with the courage and bravery of a Gryffindor that she hoped would be contagious. She did not imagine herself panicking instead. How embarrassing.
He's back he's back he's back he's back. This continuous loop of a thought was all she could hear over her own ragged breathing. He's back he's back he's back he's back—dear Merlin, am I hyperventilating? Of all the things, she thought. He's back he's back he's—
"Hermione? Are you okay? I'm sure Harry's fine, I mean he was breathing, he seemed fine, I'm sure he's okay really, Moody will fix him right up and everything will be fine—"
"He's back, Ron." She finally steadied her breathing. "You heard Harry, look how Dumbledore reacted."
"He's just freaked out, I mean, there's a dead kid on his lawn, its gotta just be that, I mean bloody hell," Ron said, frantically looking around to confirm his theory, as if someone would be holding a up sign reading "False alarm, no You-Know-Who here today, try again next time".
Maybe he's not back, she considered for a moment, her denial trying to force its way in again. She needed to be sure. "Well, I guess we had better find out."
They were finally able to see Harry much later and were assured, much to their chagrin, that Voldemort had indeed returned to the land of the living. The rest of the year passed in a blur for Hermione. She needed to warn her mother, that much was clear, but she didn't know how she wanted to do it. It was too complicated, too big, too risky. You can't just write "the Dark Lord has returned" and owl it to someone who was so tormented by him for so long. Hermione didn't know what her mother would do. She didn't want to trigger something. She didn't want the words to send her mother hurling into the madness forever. Her mother had always known about his eventual return, Hermione supposed. She always muttered it when her mind was cluttered and unclear, at least. She decided the news could wait until she arrived home. Besides, she reasoned, contacting her mother might be dangerous. They had secure methods to communicate that far surpassed owling, but with You-Know-Who's return, how could she guarantee they were safe? No, much better to wait.
Of course this decision made Hermione impossibly snippy and nearly unbearable company, as tense and worried she was all the time about it. She blamed the horrible series of events of That Night until Harry and Ron gave her some space. She tapped her foot incessantly on the train home, and nearly fled the station with just a pause for a hurried goodbye with the Weasley clan and Harry on her way out.
Hermione finally stopped rushing at the door to the first of her two childhood homes. She let herself in to find her mother in the kitchen. She broke the news. Her mother nodded. "Then our time is up," she said. "I've planned for this for years. I'm sorry that my plan, what I've decided on, is inherently selfish. I love you, Hermione, but I cannot endure him again. Forgive me." The burst of green light brought Hermione to her knees. She had worried about her mother's sanity. Clearly she should have worried about something far worse.
He's back he's back he's back he's back.
After a while, Hermione rose and gathered her things, anything she wanted to keep. Books, clothes, a single faded picture of the two of them, and the locket her mother always wore, which she had removed and placed on the table at Hermione's admission. She should have known. Look at her reaction. He's back he's back. Maybe she did know, and that's why she rationalized putting it off. Hermione raised her mother's wand. He's back he's back he's back. The house ablaze, she watched the fire consume her home, stealing this last moment until sirens blared in the distance. She slipped away and traveled to the Grangers.
A week later, she reached out in hopes of involving herself more in the wizarding world. She was truly a Granger now, she supposed, but she couldn't bear being a Muggle as well. Her request was granted, and so Hermione found herself traveling to Number 12 Grimmauld Place, London, for the remainder of the summer holiday.
