This is an adventure outline I worked up for a Trail of Cthulhu one-shot that I had planned, set in modern day Leeds.
|Y'golonac - by Finn|
It's quite open ended after the first set-up scene which exists basically to show the investigator someone who had gone a long way down a particularly dark path... and then to set their own feet on that same path. There are hints in there of investigative avenues that Keepers can flesh out as they wish and a variety of sketched out NPCs that can become allies, adversaries or some combination of the two as things go on.
While suggestions are given for potential end points and solutions nothing is set in stone. My own style would be to run this and see what paths the player's choices led them down and adapt accordingly.
I hope it is of interest and whether it is of use in its current format or not I hope it may perhaps spark an idea or two that you can use.