I think I might possibly, maybe, potentially, perhaps have decided on which story I'm writing for NaNoWriMo in November. And it's only the 21st!
It's a fantasy story -- sort of a 'Lord of the Rings' setting.
It starts in modern time, however, and as a result of the tried-and-true stumble through a hidden portal, the heroes (Patrick and Melissa, next-door neighbours) end up in a fantasy world.
They learn that Rebecca, Patrick's late sister, was practically a national icon there -- rather a Queen Elizabeth I. According to the people, she saved them from their enemies several years before, and in gratitude for her service, they gave her the key to the healing spring (yet to be officially named) and told her to hide it where their enemies would never find it.
When they discover that Rebecca was Patrick's sister, they beg him to bring her over because there is now a devastating plague (my characters do seem to run into those, don't they?) that is threatening to wipe them out and they need her to access the healing spring for them. Upon being told that Rebecca is dead, they name Patrick Rebecca's successor and send him and Melissa off on a quest to either find where Rebecca hid the key or find (and enter) the healing spring itself. Naturally this isn't easy, and they run into several pitfalls and must jump through several hoops along the way...