This is the fourth and final quest where you help Antó. It unlocks after completing the previous quest, "Under Attack." To start it, speak with Antó, who is waiting for you at the marketplace.
Edward must assassinate Kenneth Abraham and recover his Templar key.
First, you'll need to tail two officers to find out where your target is located. Stay behind them at a safe distance and listen to their conversation - after a moment, you'll learn where you should head. If they spot you, you'll have to kill them and find a note on their bodies.
Follow Anto to the estate where the party is taking place. This is a restricted area, so after passing through the breach in the wall, hide in the tall grass.
If you listen for a moment to the conversation between two soldiers standing by the alarm bell, you will learn that your target is located somewhere near the buffet.
Hint:
Go through the next breach in the wall to the right. Anto will climb onto the roof of a nearby building and then onto its tall chimney. Follow his lead and do the same.
From the top, you can safely scan the area where the party is taking place and pinpoint Abraham's exact location. The area is guarded by a quite large number of soldiers.
Leap down into the hay wagon beneath the chimney and use the tall grass to move to the right side. There you'll find a gap in the fence through which you can slip onto the grounds where the party is taking place.
The soldier talking to the woman on the left won't notice you, so sneak up to the soldier in front of you and assassinate him.
Climb the wagon leaning against the wall of the building in front of you to reach its roof.
Move around the roof and leap onto the wooden wall post near the buffet table.
When Abraham approaches the table, you'll be able to air assassinate him. A cutscene will trigger in which you'll obtain the Templar key.
Immediately after the cutscene ends, the alarm will sound and nearby soldiers will try to kill you. Quickly leave the estate grounds through the east gate, escape the area, and drop aggro. Alternatively, kill any soldiers who stubbornly try to chase you down.
Once you lose the pursuit, return to Antó - who will be waiting for you in the bureau - and speak with him to finish this quest and complete the whole line.
