In the Library you meet with a bloke by the stacks who tells you about some other bloke who has turned the music up loud... He thinks we should find out where the music is coming from and perhaps why?
When we arrive at the apartment it turns into a Safe Zone - and inside there is a very odd man whose thing is telling the future for people - you explain that he needs to shut off the music - with no effect.
He wants you to get him x6 Night Herbs from the River - great, another Night Mission!
Basically you want to go to the nearest Safe Zone then rest until night, then ninja out to the area and pick the herbs - carefully...
Once you have them picked head back to the Safe Zone and rest until morning, then head to the marker on the map to deliver the herbs and complete the quest.