And so my humorous Fantasy Detective story was born. I had the detective, the setting, a pretty good magic system and a locked room puzzle with a difference. Then things started to go wrong. Small things at first - there was something missing with the main character. He was 90% there but something - something I annoyingly couldn't put my finger on - didn't gel. Then there was the magic system. It started off great but as I fleshed out the detail I realised I'd made it too powerful and suddenly my tight plot had several large holes in it. So I revised the plot to take that into account and suddenly the short story grew into a novella. Extra characters arrived, extra plot twists. I was 16k words into the story and still the end was a long way off. And worst of all I didn't feel enthused enough to continue. The story had grown from funny and tight to amusing in parts and rambling.
So I put the story aside.
Then last week I had one of those lightning flash ideas. The really cool idea that lands in your head pre-formed and begging to be written. Again it was a comic Fantasy detective but this time I could see it working. The magic system was similar but far tighter, and the premise moved the focus from the puzzle to the characters and procedure. Which, I think, is the trick of writing short mysteries. If you focus on the puzzle - and you're anal about making sure your puzzle is not only clever but only has one solution - then the page count can multiply. The puzzle consumes you, you feel the need to add red herrings, plot twists, cliffhangers and before you know it you're halfway to a novel.
So, this time I've kept the puzzle element simple and used it as a vehicle to show off the characters and setting. So far I'm 3,600 words in and the end is very firmly in sight.