There is a mysterious artifact that is causing evil creatures to appear and begin attacking towns and civilians. The longer you take to solve the mystery, the more towns (that you could not save in time) end up in ruins.
Time is ticking! ;)
Concept shamelessly ripped off from the awesome gem of a game called StarFlight where I played the Sega Genesis port from 1991. Nintendo shamelessly plagiarized this concept for Majora's Mask but at least it was executed well in that game.
No use letting such a great game idea go to waste! Also you can add in some stuff like building up a 'defense force' (costing you both time and in-game currency) but allowing certain areas to survive longer and thereby getting a better ending. However you cannot save everyone and have to pick/choose (also allowing for replayability).
If you are interested in talking shop and discussing game design, I'd love to chat with you via Discord if you'd like to join up in my gaming/social server called FreshGaming. I've already made friends with some indie devs and wouldn't mind adding to the party :)