Wrestling with theme

I am plotting for the Extreme Planets short story, and it’s all going well, except for the theme.

You know when you are trying to remember something, and you just can’t?   That “tip-of-the-tongue” feeling?  That’s what I have with my theme.

Luckily I can still write without having my theme in words.  But still.  The sooner my brain lands on the theme, the better.  I feel incomplete without it.