"Hey, Doctor?"
He stopped working an pushed up his googles.
"Yes, Clara?"
She looked a little confused and uncertain.
"What is bad wolf?"
"What?" He asked.
"Well, back on Gallifrey, when we were with the younger yous, they mentioned the words bad wolf."
He pondered for a few minutes. He still felt guilty over her. Rose. The younger him had been so naïve. He thought that he could force her to be happy. He knew that he couldn't do that with anyone, least of all her.
There had been times when he had found weak spots in the wall separating them. He had thought about just going to watch her. He never had and he had always wondered what became of her and the other him.
They would be old by now. Maybe they had children. A little blonde boy and a brown headed girl. Maybe one of the children was ginger. That would be ironic.
But he had always been able to stop himself, because what if she wasn't happy? What if he had simply caused her even more misery? What if every day she woke up and saw the other him and remembered her life traveling and adventuring and missed it. Every single day.
He couldn't handle that.
He sat there thinking about it for minutes before finally Clara said something.
"Doctor? Are you okay? You don't have to answer me."
"No, no, no. I'm fine. Bad Wolf was one of my companions. She was a girl named Rose Tyler."
She looked at the sadness in his eyes.
"What happened to her?"
He sighed heavily.
"I left her somewhere. I left her somewhere and I couldn't ever go back."
She was confused.
"Why not?"
"What?"
"Why couldn't you ever go back?"
A tear formed in his eye. Clara looked upset.
"I'm so sorry. Don't answer that. I'll just-"
"No. It's fine. She was trapped in an alternate universe. She escaped and I took her back because I hoped she would be safer and happier there than she would be with me again. I left her there with another man. Someone she could grow old with."
He wiped tears from his face. Clara was surprised. She walked over and hugged him.
"I'm sorry. I didn't mean to make you cry."
He hugged her back.
"It's okay, Clara. It's fine."
They stood there for a while, hugging while the Doctor cried on Clara's short shoulders. She was shocked at this rare show of negative emotion. The Doctor never showed her his true feelings, although she could usually see them just below the surface.
After a few minutes he stood up and wiped his eyes.
"I'm going to go down to the library for a little while."
"Okay." She said.
She watched as he walked off, his hands in his pockets and his frame haunched. She hadn't known how important this would be to him.
But no one could know exactly what could be important to a man who was over a thousand years old.
She stroked the console for a moment, just as she had seen him do over a thousand times, and then she headed down to her room to sleep.