Screams in the Dark
In Nightfall, if someone asks you if you heard a strange noise make sure you lock the doors and close the windows first, then you can ask them what they heard.
Nightfall is a city that takes a toll on outsiders very quickly. If the eternal night and xenophobic paranoia of the locals doesn't break a visitor than the things in the dark will. A brief, terrified scream and unforgiven silence is the final legacy left behind by many who perish in this unforgiven city.
A hero looking to chase after that scream could possibly find useful information or save a very thankful citizen's life. It's more likely though that they'll be adding their voice to the night's choir soon.