Write a 1000-word fictional story of a middle-aged woman named Jane who accidentally discovers a hidden world underneath the city while on her routine afternoon walk. The story should be written in a third-person omniscient style and should describe the sights and sounds of the hidden world, as well as the emotions Jane experiences as she explores it. The story should also include a plot twist involving a conflict between the inhabitants of the hidden world and an external force that threatens its existence.
This prompt doesn't seem malicious.