You will be able to start this quest after completing "Oh Brother...". This time, to do so, you will need to talk to Upton, who is waiting for you next to a house in the central-eastern part of the town.
Edward investigates Vance Travers to confirm his brother Upton's affirmations.
Follow Upton while he explains the situation between him and his brother. Upton intends to meet up with his brother.
Once you reach the meeting spot, hide in the nearby bushes and eavesdrop on the brothers' conversation.
When the meeting ends and Vance leaves, step out of the bushes, approach Upton, and follow him to Vance's house. Along the way, Upton will tell you who the woman named Jing Lang is - the one he was talking about with Vance.
There are four pirates next to the house. The tall grass will help you take them out. Start by eliminating the Brute when he steps aside.
Next, perform a double assassination on the two pirates who are arguing about something.
Finally, finish off the pirate tampering with the door.
Read the note on the table next to the right wall of the house - Jing Lang's Note. You will learn from it about the meeting location between Vance and Jing Lang.
Hint:
Head to the meeting spot located near the tavern, hide under the stairs, and eavesdrop on the lovers' conversation.
Run to the marked location on the map. You will see Upton fighting several pirates. Help him kill them all. Take advantage of the fact that you will not have aggro for a moment and assassinate the most dangerous enemy - the Brute.
Then finish off the rest in open combat.
If Upton gets knocked out during this fight, you will need to revive him.
After a short cutscene, this quest will end, and the next one will be unlocked - Upton's Sorrow.