It was Pompeii, but not as they'd left it. Standing in the midst of the wreckage, the Doctor could feel his two hearts heaving great sighs of regret. Anything I do just makes it happen. His hearts were breaking as his dark, weathered eyes moved across the wasteland. Just as he could feel his throat constricting, the dilemmas of a lonely god, the Doctor felt a warm sensation upon his shoulder. He looked to his right and saw that Donna Noble had lain her hand across him.
"I understand, Doctor. You can't save everyone." Her eyes revealed that she knew more than he gave her credit. It seemed that, though the two had been apart for so long, there was nothing that stopped her intuition. And with those three small words that the Doctor had said all too often, Donna provided him a respite. "I'm so sorry." She need say nothing more. He was the Doctor and he had all of Time in his hands. He couldn't fix the whole universe, but that didn't stop him from trying.
She blinked through bright eyes and took his hand. "Come, Doctor, take a walk with me." It was as though her other half had returned. With the Doctor, she had a purpose - she saved the whole of creation. Time and Time again, she would prove herself to him. He couldn't leave her behind. He just couldn't. The Doctor needed someone there, someone to stop him. In his absence, she'd learned about the Valeyard and it frightened her. They couldn't be one and the same. They just couldn't. "Let's have us a talk." Donna Noble was serious as she maneuvered through the ash-ridden wasteland that had previously been a staple in Italian civilisation.
As she led him through the wreckage, he could feel Time stand still for them. Without anyone to save but themselves, there was nothing to do but accept that Donna Noble was back. She was back and she could contain him. The Doctor knew he couldn't always win, but be damned if he didn't try! However, with Donna around, he never viewed himself as the Timelord Victorious. The Doctor shook his head slowly. He had made so many mistakes.
"Donna. . ." The Doctor let her hand fall, sliding his own into his coat's pockets. "Oh, Donna Noble," his voice was calm, as if he'd always known that they would be reunited though he could not fathom just how. "You truly are the most important person in the universe." You could have stopped me. Would he have failed to save Donna in the same circumstance? She was human, she had feelings and emotions, never limited to the laws of Time. Humans didn't follow the rigorous laws set forth by the Gallifreyans and by that, never had the universe in their minds. But here was this flaw in the system. Donna Noble was both human and Timelord. She should have burned up, but she didn't. She was alive.
He shook his hand, sitting upon what appeared to have been a table. He knew he had gone too far. Even going back to make certain Donna was alright was too far. While he knew that she would never give up searching for him, the Doctor suddenly regretted having gone back to find her. He was lonely, that much was true, and desolate after losing Adelaide. It was his downward spiral which sent him back to Chiswick.
She sat beside him. Though itching to ask what he'd done since leaving her behind, Donna knew it would come in time. The Doctor needed his time just as much as, if not more than, everyone else. The TARDIS, all of Time, and an empty universe is all he's had to look to. It was impossible for any human to imagine. But she wasn't just any human. She was Donna Noble and she could feel the screams echoing through his mind. She could hear the pain masked by his everyday words. Most of all, she saw the End of Time and her heart broke.
Disclaimer: DW doesn't belong to me, no matter how much I wish it does.
A/N: This was written just after Waters of Mars. I let it ruminate for a few months (as you can probably tell). My computer crashed a few months ago and I just recovered this. And I didn't edit anything from the initial write.