The thing about being a Time Lord is that time exists as a somewhat malleable substance; that it is entirely possible to observe the whole fabrication of time itself in a second. The moment when Rose's fingers slipped on the lever and she lost her grip on this reality, time slowed down. He watched the nanoseconds trickle by with no comprehension of anything other than blood-curdling, heart-shattering horror, watched as his pink-and-yellow human, the only woman he ever dared to love with all of his two hearts, was ripped from this Universe, taking his soul with her.
Time resumed normal speed once she was gone. Of course, it still felt like it took an eternity without her shining presence at his side, but he learned to stop thinking about her every second of the day. (She continued to plague his thoughts by night, however, and on those rare occasions that he did sleep, he dreamed of nothing else.)
Donna was a good distraction, he decided early on. If Rose was the love of his too-long life, Donna was his best friend. He never understood why she didn't see her own value at all, when she was clearly so intelligent and spunky and full of life.
"I'm nothing special," she said one afternoon for the hundredth time, as the two of them examined a truly bizarre, beetle-like alien that fed off time and managed to create an entire parallel world around Donna herself.
"No you're not, you're brilliant," the Doctor said fondly, as he had taken to doing lately when she uttered self-degrading phrases in his presence.
"She said that," Donna said suddenly, and the Doctor looked up. Her face had gone blank and pensive.
"Who did?"
"That woman." Her eyebrows furrowed as she thought hard. "Oh, I can't remember."
"Well, she never existed, now," He said, concern etched on his face as he watched her struggle with her own memories of that parallel life.
"No, but she said—she said the stars… she said the stars were going out."
"Yeah, but that world's gone."
"No, but she said it was all worlds! Every world… She said the darkness is coming, even here."
Well that didn't sound good. "Who was she?" he asked. There couldn't possibly be many women, either in this world or a parallel one, who could see the future or have any real understanding of the vastness of the Universe.
"I don't know."
Well, he could think of one woman who just might fit the bill. But she was lost. Never to return, not to Donna's world nor this one.
Because jumping between Universes is impossible.
Still, he felt he had to quash his own theories to put his mind at ease. "What did she look like?"
Donna thought for a moment. "She was blonde…"
Both of his hearts stopped for a second. No, it had to be a coincidence. But what if it wasn't?
"What was her name?" His hearts were beating faster now. His mind started racing, because the more he thought about it, the more he realized it could not be a coincidence. There was no way someone, anyone else could know…
"I don't know!"
"Donna, what was her name?" If he didn't know soon, he would probably explode.
"But she told me… to warn you… she said two words…"
A thousand word combinations ran through his head, some in different languages and from different planets, some even in Gallifreyan though he knew those were impossible. His voice grew frantic. "What two words? What were they? What did she say?"
And then time slowed again. Donna paused, a pause that seemed to last a thousand years, and then she opened her mouth. As she spoke, the sound of each consonant and vowel rolling off her tongue, his hearts started to swell with emotion. Each fraction of a syllable brought him closer and closer to the verification that he so desperately needed, because if Donna said the two words he achingly hoped and also dreaded she'd say, it could only mean one thing.
"Bad Wolf."
Rose.