"No."

The Doctor said the words before he even thought them. It was generous, what Jack was offering. More than just offering, he was practically giving it to him. There was no doubt in the Doctor's mind, now, that Jack told the truth when he said he thought they were close. It took a lot of trust to open one's mind to another.

And Jack wouldn't have known the Doctor could if he hadn't told him. Or shown him. The second thought was infinitely more terrifying than the first.

"I can't," he said. "I just can't."