This article (New interactive “Murder Map” Reveals the Meanest Streets in Medieval London) showed an old map that indicated where the most dangerous parts of town were and it gave me an idea. Something like Minority Report (2002) where murders are predicted but instead of these premonitions coming from a group of sci-fi Precogs, police investigators work with a geographer or cartographer to predict and map the areas of future crimes.
What I love about the idea of map is that it is visual. It is something that can be use to show and not just tell. If the map is done right, the audience will figure out the “murder” pattern along with (or sometimes before) our protagonist does.
John Snow figured out which of two pumps in town were the source of the cholera epidemic in London on 1854, using a map to identify where people lived and which public water pump there were using.
What about a criminal cartographer that saves detailed maps of their crime?
A murderer has a specific pattern to their crime that the detectives can’t decipher but a skilled geographer can.
Who wants to talk more about how you can use this idea in your current or next story?