"I know."

Fy slithers over to give her a hug.

...sure, snake hug.

Well, he can't do it.

She pats Fy a bit. "I don't usually tell people I've got a sister still alive. Some people I just don't like them being aware of any specific living drow who wouldn't see 'em coming, you know?"

Nodnod.

"So keep your mouths shut."

"Of course."

"Thanks."

"If there is anything we can do you should let us know."

"Help me get the Starstone."

"Well. We can make you lots of money and get you into some fights."

"'Preciate it."

Mahdi catches someone abovedeck that afternoon. 

"This gives me a - line, right, where they could be," he says, drawing it on a map. "And now we have to go fly the whole thing immediately and if they're moving too fast we'll lose them and I'll have to do it all over again."

"Perish the thought."

"I can be packed in ten."

"See you then."

She meets them ten minutes later with all her stuff.

They are also packed and ready to head out.

On the carpet they go. "How d'you triangulate like that from a scry?"

"Angle of shadows. - do you know anything about how the movements of the world and sun work, it occurs to me that drow don't really have any reason to -"

"I was in school for seventy years, we may have covered it, but that doesn't mean I recall."

"So the world orbits the sun. It's hard to get an intuition for it because it only works the way it does since they're both absurdly big and absurdly far away. The seasons are caused by the world being tilted with respect to the sun, which affects how the light hits it, and light hits different places on the surface of the earth at different times, so if it's noon in Sothis it's going to be noon in a bunch of other places -" he makes himself an illustrative illusion to help - "on a line, like this. And as it stops being noon, the shadows get longer. To figure out where someone is you need to be able to measure how long a shadow is in the scry, and it needs to be the shadow of something whose height you approximately know - like a person. Then you can calculate how far past noon it is, where they are, and then you can draw a line that shows all the places they could be."

"How do you mean the world is tilted? It's a sphere, it's the same all round."

"Relative to how it's spinning around the sun, I mean." He frowns at his illusion for quite a while until he can get it to show this.