Thief of Time - Stay

'Good. Everything I have just said is nonsense. It bears no resemblance to the truth of the matter in any way at all. But it is a lie that you can... understand, I think. And then, afterwards-'

'You're going to go, aren't you,' said Susan. It was not a question.

'I will not have enough power to stay,' said Lobsang.

'You need power to stay human?' said Susan. She hadn't been aware of the rise of her heart, but now it was sinking.

'Yes. Even trying to think in a mere four dimensions is a terrible effort. I'm sorry. Even to hold in my
mind the concept of something called "now" is hard. You thought I was mostly human. I'm mostly not.'

He sighed. If only I could tell you what everything looks like to me... it's so beautiful.'

***

The Thief of Time - p335