Next Big Thing meme

I'm usually shy to talk about work in progress, but I've universally enjoyed reading others' answers to these questions--very much so. I was tagged by cafenowhere and implicitly tagged by ann_leckie and the other souls who invite anyone to join in, so here goes.

What is the title of your book?

I call it Pen Pal

Where did the idea for the book come from?

It came from combining two things: a dream about someone being trapped/held/serving in a temple above a live volcano, and an image of a group of...