Just where exactly IS Neb?

Doing the illithium quest in Baldur's Gate 2 once again, I got to thinking about the child-killing bastard of a gnome I had to hunt down to finally get my reward. The way everyone talks about him, he was apparently supposed to be in the first game - yet in spite of having played through that one a countless number of times, basically going through everything and doing everything, I don't remember ever encountering him.

So where is he?