Thanks for a great prompt ! Here's my entry, hopefully it's thriller-ish enough 😁
It actually gives me the opportunity to write a sequel to a post I wrote a while ago which I think has the potential to turn into a bigger story, but it should still work as a standalone (if it doesn't, let me know !)
https://peakd.com/hive-199275/@alonicus/the-secret-of-doktor-von-falken