This is the final quest you will perform for one of your officers - the Padre. It begins automatically after completing the "If Thy Right Hand Offend Thee" quest.
The Bishop has built his stronghold in Kingston. Edward follows the Padre to tear it down.
Head to Kingston, go to the marked location, and sit on the bench you find there. Once dusk falls, Padre will appear as well.
To get the first clue head east and Examine the poster board note.
Head south. On a small dock, two women are talking. Get closer to eavesdrop on their conversation.
Head east. At the dock near the large barn you'll meet two men talking about the invitation letter.
Hint:
Follow the marked man until he stops inside the barn and then pickpocket him to get the Invitation Letter.
Go to the location where Padre is waiting for you and talk to him to report what you have learned.
Follow Padre until you reach the point where you split up. Along the way, Padre will tell you about the Bishop—what he was like and how he changed.
Hint:
Four soldiers are guarding the entrance to the forest. Get rid of them in any way you like. For example, you can start by shooting a sleep dart at the marksman on the right side, and while the two guards in the middle get distracted by what happened, quickly and quietly finish off the guard on the left by the crates. Afterward, depending on the situation, kill the remaining guards.
Enter the forest and move forward, and after a short while, you will see Bishop and the soldiers accompanying him.
You must defeat them all. The most dangerous enemies are the Brute and the marksman standing on either side of Bishop. You can sneak up on them a bit from the left side and eliminate as many as possible with pistol shots. The Padre will join the fight as soon as it begins.
After defeating everyone, approach Bishop and talk to him...
...to trigger a cutscene featuring a confrontation between Bishop and the Padre. Afterward, this quest will end, and you will receive a reward for completing it - Small Goblet (Trinket).
Small Goblet
Perk: Increases the amount of healing from food, drink, and remedies.
