The Big Dig The Big Dig is a side quest in " Fallout 4 " . Detailed walkthrough . The Sole Survivor receives the quest after speaking to Bobbi No - Nose in a backstreet in Goodneighbor . She says that she ' s planning a job that requires discretion , not sharing many details at first . From here , one needs to go down into the Dig , a tunnel starting at Bobbi ' s house basement and help the diggers fight the mirelurk s . After , she asks the player character to meet her in Diamond City , where she reveals her plan to break into the Diamond City strongroom under the mayor ' s office . In order to do this , Bobbi requires assistance in freeing an old associate , Mel , from the security office . There are several ways to free Mel : pickpocket a key , steal a key from the nearby office , hack the nearby protectron to kill the guards , or bribe the guard nearest him or convince him to let Mel go by passing a medium or hard persuasion check . The guard that can be bribed or persuaded is the one that moves around between Mel and the office nearest to the jail . Crimes will of course result in security turning hostile ( and possibly one ' s active companion ) , however , using dialogue will not turn them hostile ( even if the threaten check fails ) . To the left of the cell is the office , inside the Survivor can steal the key from the desk , then sneak to the right side of the cell . When the guards are not looking unlock the cell with the key and meet Mel outside . Tell Mel about the job and meet him at the Dig . Gathered at the dig site , Mel has prepared an eyebot named Sonya to blow through soft walls in the tunnel with sonic resonance . The group begins traveling through old metro stations and basements filled with feral ghouls and more mirelurks . At the first available opportunity to tell Sonya where to blast , it is possible to blow open the wrong path , leading to a dead end with a mirelurk king as well as a leveled set of power armor . Mel will frequently express his doubts about the tunnel actually leading to Diamond City , that the team is heading too far south . After they make it to a cavity underneath the strongroom and blow the ceiling , sacrificing Sonya , it is revealed that it ' s not Diamond City ' s strongroom but a secluded storage room at NH & M Freight Depot owned by Hancock , Goodneighbor ' s mayor . The room is filled with the mayor ' s henchmen . The player character is subsequently given the choice to persuade Bobbi to leave and surrender , kill all the guards and stay with Bobbi , or betray Bobbi and kill her for the mayor instead . ( If the player character enters the room wearing headwear incorporating a targeting hud , Fahrenheit and her men will be automatically hostile , forcing the player to kill them to continue . If the headwear is still worn after finishing the quest by getting paid , Bobbi will also immediately turn hostile and attack . ) If the player character persuades Bobbi to leave or betrays her , Fahrenheit will reward them with a legendary minigun with incendiary bullets , Ashmaker . Additionally , Hancock will become available as a follower . Even if the player character kills Fahrenheit and sides with Bobbi , Ashmaker can be looted from Fahrenheit ' s corpse and Hancock will still be available as a follower after finishing Hancock ' s follow up quest of killing Bobbi .