(urth) The Nebraskan and the Nereid

[Andrew Dubbeld]

I was recently reading through Endangered Species, and came across The
Nebraskan and the Nereid. It all seems relatively straightforward, right
up until the end, when Dr. Thoe Papamarkos dives into the sea, leaving
her things behind, including a canteen which seems to contain salt
water, and suddenly there's a dead woman on the beach.

"She smiled, then when he realized he could not convey the news of a
tragic death with any decency in his inadequate Greek. Thoe would have
to tell them. He would wait until someone came."

I'm left with a couple of questions that perhaps someone on the list
might be able to help with:
- Who is the girl? Is she the woman Sam's seen in the water earlier?
- Where did she come from and why is she dead?
- The introduction to Endangered Species hints that there's either love
or sex in this story, but where?