Return a dangerous necromantic scroll to the Net of the Mask.
Scarlett should go up on the northwestern Inner City Rooftops, where she will discover the body of Balthazar. The easiest way there is probably to enter the Tavern, climb the stairs in the back, and go out onto the roof, then make her way westward (dealing with Rogues as necessary.) (Alternatively, Scarlett could use any of three windows from private houses to get out onto the rooftops; see Inner City Rooftops for a complete map of access points.)
Scarlett will get this quest automatically after she discovers Balthazar's body lying on the Inner City Rooftops. After she deals with the Living Statue, Nox will approach her and tell her that the scroll is dangerous and she needs to return it.
Scarlett needs only to go back down to the street (through the Tavern or any of the three windows mentioned previously) and make her way to the Net of the Mask guildhall. (It doesn't matter which Guild Scarlett joined.) Speak with Aeris and return the scroll. (Click on map to enlarge.)
(Scarlett we'll eventually have at least one good reason to go up to the rooftops: The Pathway to the Claw quest will require she visit Tusker at his rooftop hideout. She may also be undertaking the Clear Sky in the Inner City quest.)