- The merchant will insist Scarlett have a Reputation of at least 50. This means she will have to have completed one or two other optional Quests beforehand.
The Warehouse Merchant offering the quest is seated at his table in the northern part of the Amphitheater. Scarlett won't be able to complete this quest until she has earned access to the Arsenal District, which will take some time. Aside from that, this is a very easy quest to complete.
Once Scarlett has finally arrived in the Arsenal District, she will find Gregorius [(also known simply as The Doctor) on Shade Street. He's on the same level as the entrance to the Inner City, about halfway along Shade Street. The door to his clinic is right beside where the trader Dominicus now sells his wares. (Click map to enlarge.) Just walk in and give him the package. (It's not necessary to report back to the Warehouse Merchant to complete this quest; the delivery itself suffices.)