Reformation

Reformation is a main quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
During the quest The Way Life Should Be when confronting DiMA about killing and replacing Captain Avery, the Sole Survivor can agree to keep it secret. After that, DiMA will suggest to the Survivor a plan about replacing High Confessor Tektus with a synth to make peace between the factions. Agreeing to the plan will start the quest. The Survivor then has to find the old High Confessor, Martin's holotapes from his hideout and bring them back to DiMA. The Survivor will then go talk to Tektus and assure him that the old confessor Martin is going to come back and take over his position by showing him a faked holotape from Martin. The Survivor will then meet Tektus in the command center and kill him. Alternatively, the Sole Survivor can pass a medium speech check to make him flee (if you haven't done enough quests with the Children of Atom to win his trust, he will come with two guards and you would need to pass a high speech check to make him flee). If Tektus and his guards are killed, their corpses must be stashed in the hole in the wall. The Sole Survivor then returns to Acadia and sees DiMA talking with the new synth High Confessor. DiMA will reward the Survivor with 1500 caps and Protector of Acadia perk. The Sole Survivor will then get the miscellaneous quest Speak to High Confessor, which will reward the player with Atom's Bulwark. Additionally, the Survivor can return to Far Harbor and witness a meeting of the townsfolk, where Avery informs everyone that they have made peace with Children of Atom. Avery will give the Survivor 1600 caps when talking to her.