Reunions Reunions is a main story quest and achievement in " Fallout 4 " . Detailed walkthrough . Dogmeat finds the scent of Kellogg and leads the party out of Diamond City , stopping at a small pond to the south . There is another San Francisco Sunlights cigar which needs to be picked up and shown to Dogmeat to continue the search . He follows the trail along the railroad tracks , where mole rats and other creatures may be encountered . At the underpass , Dogmeat will stop in a doorway . In the nearby area there are signs of Kellogg ' s blood , showing the bloody rag to Dogmeat will continue the search . The trail continues across a bridge to the remains of an assaultron that can be spoken to for more clues . Depending on which way Dogmeat leads the party through the forest , there is a possibility they will run into a deathclaw sleeping in a small cave . On the outskirts of Fort Hagen , there are bloodied bandages on a fence that are the next clue for Dogmeat to follow . Eventually the trail leads to the entrance of the fort where the doorway has been blocked . Enter Fort Hagen , either by a roof hatch , or through an exit door in the underground parking lot . Inside the facility are numerous synth s and automated turrets guarding the building . The energy weapons bobblehead can be found in the kitchens of the command center . Deep in the facility , Kellogg begins talking to the Sole Survivor via the building ' s intercom , advising them to turn back . Eventually the Sole Survivor comes to an office with a sealed door where Kellogg concedes that the Sole Survivor won ' t leave and opens the door so they can talk . During the conversation , Kellogg will reveal that Shaun is being held by The Institute , and thus out of reach . The conversation will end with both parties stating that the other must die and a fight breaks out . After Kellogg and his bodyguards have been killed , a nearby terminal will reveal clues on where to continue the search for Shaun . The password for the terminal can be found on Kellogg ' s body , along with his cybernetic brain augmenter which is needed for the next quest , Dangerous Minds and his unique gun , Kellogg ' s pistol . The terminal will unlock the security doors which leads to the exit . Note that a doorway which led into this final area will be closed and remain locked once the battle with Kellogg is started , preventing backtracking into the fort . However , the exit elevator becomes available at the opposite end of the same hall . Upon exiting the fort , a short scene plays where the Sole Survivor witnesses the Brotherhood of Steel arrive in the Commonwealth in full force , having traveled from the Capital Wasteland on board the Prydwen , which acts as their mobile base . Several Vertibird s will escort the Prydwen as it travels across the Commonwealth . The Brotherhood will announce their arrival via a loudspeaker and state that they are coming with peaceful intentions . This starts the quest Reveille if you ' ve not dealt with the Brotherhood before , or Shadow of Steel if you have completed the Act 1 quest arc for the Brotherhood . Back at the Valentine Detective Agency , a conversation with Nick Valentine and Piper will complete the quest . If Nick was your partner against Kellogg , after speaking with you , he will direct you to talk to Piper at Publick Occurrences , where the next major part of the main storyline will begin .