He couldn't do it.
No matter what Voldemort's terms were, Harry couldn't imagine killing someone – anyone - else. Bellatrix might be a monster and responsible for his godfather's death, but even so, he didn't want to kill her.
Perhaps more accurately, he didn't want to stain his hands with blood. If only someone else could kill her instead.
If Harry killed Bellatrix, then he would never be able to go back to the way he was.
So when the Dark Lord came again for his answer, he told him no. Voldemort smiled, terrible white lips gaping open like a bloodless wound. He thought that Voldemort had been happy.
He played the waiting game again. The books were back, but Harry had no interest in reading them now. He waited, tense and dozens of horrifying images playing through his head, for news. It seemed like hours before Voldemort came again.
He brought a Pensieve with him. The thing was already shining with someone's memory, and Harry could make out the outlines of the door to the Room of Requirements.
He dove in, eyes wide open.
It felt like a dream, because Harry couldn't quite take it in, couldn't completely accept that this was what had happened.
Bellatrix was a powerful witch, too strong to be stopped by the likes of a few peaceful harmless children, whether or not they could do magic. He registered that she was alone and wondered if Voldemort had decided to send her on a suicide mission.
But of course, if Bellatrix had died then Voldemort wouldn't have her memory.
It looked like Bellatrix had some destination in mind. She was going up the stairs, past rows of portraits that she immobilized swiftly, cursing all students and staff in her way.
She came to the portrait of the Fat Lady and blasted it open. Harry stared, heart in his throat. He knew what was coming now.
Ron and Hermione were sitting in the Gryffindor common room. Harry felt warmer at the familiar, comforting sight even as he knew what was about to happen. They were really helpless against Bellatrix.
When she pronounced the words "Avada Kedavra," Harry closed his eyes. Maybe it would be better to never see again?
"Hello, Longbottom. Would the baby like to see his parents?" she taunted and his eyes snapped open.
"If Harry was here-" Neville began.
Harry wasn't there, even as Neville screamed and writhed and begged under the Cruciatus. He couldn't save anyone.
Before it was too late for Neville, Dumbledore swept into the room and Bellatrix immediately swung around to face him, grinning madly. It was too late for Ron and Hermione.
Before she portkeyed out, Harry gazed at Dumbledore's face. Maybe if he memorized that look, those eyes, then his dreams wouldn't be filled with the deaths of his best friends.
Harry came out of the Pensieve, gasping for breath. He had never felt this way before. He looked up into Voldemort's cold red eyes and moved in to hit him.
He wanted to hurt this man, this monster, who had been responsible for so many deaths, so much pain. He wanted to kill him, but hitting Voldemort was like hitting smoke. There wasn't any resistance, even as Harry scratched and punched and kicked.
Maybe he really was less than a true man.
Harry paused, unable to continue. What was the point anymore? And his best friends were dead, just because he had been too cowardly to let his hands get bloody.
Voldemort stepped back, created a Patronus – a smoky horse, Harry noted. It galloped off.
When Harry saw Bellatrix's face – first adoring as she gazed at her lord, then startled and malicious as she glanced at Harry – he had no more hesitation.
"Avada Kedavra." Harry Potter could never go back home – there was no home left.
