The Big Dig

The Big Dig is a quest in Fallout 4.

Quick walkthrough

 * Meet Bobbi inside
 * Join the dig
 * Exterminate the Mirelurks (0/3)
 * Talk to Bobbi
 * Meet Bobbi in Diamond City
 * Get Mel out of jail
 * Recruit Mel
 * Meet the gang in the Dig
 * Dig to the Strongroom
 * Meet with the gang in the basement.
 * Get out of the basement
 * Enter the Strongroom
 * Side with Bobbi or Fahrenheit

Detailed walkthrough
The player character receives the quest after talking to a woman named Bobbi No-Nose in a backstreet at Goodneighbor. She says that she's planning on breaking into the Diamond City strongroom located under the mayor's office. At first the player character needs to go down in The Dig, a tunnel starting at Bobbi's house basement and help diggers fight mirelurks. After, she asks the player character to meet her in Diamond City and help free another member of the heist team, Mel.

Freeing Mel can take one of several forms, bribing the guard nearest to him, pickpocketing a key, setting the protectron behind him loose to kill the guards or passing a moderate or hard persuasion check. It may be difficult to find the right guard as there are no distinguishing characteristics. Breaking him out with lockpicking will likely result in security becoming hostile. To the left of the cell is the office, inside 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. If the guards spot you they will become hostile.

Finally, the team goes into the tunnel, traveling trough old metro stations and basements filled with feral ghouls and more mirelurks. Mel will frequently express his doubts about the tunnel actually leading to Diamond City, as the team is heading too far South. After they make it to a cavity underneath the strongroom and blow the ceiling with the help of Sonya, a modified eyebot, it is revealed that it's not Diamond City's strongroom but a secluded storage room owned by John 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 persuades Bobbi to leave or betray her, Fahrenheit will reward them with a legendary minigun with incendiary bullets (+15 fire damage); Ashmaker. Additionally, John Hancock will become available as a follower.

Even if the player character kills Fahrenheit and sides with Bobbi, John Hancock will still be available as a follower after finishing Hancock's follow up quest of killing Bobbi.

Behind the scenes

 * The quest name is a reference to The Big Dig, a massive public works infrastructure project constructed in Boston that involved the building of various highway tunnels under the Downtown area.
 * Another four wooden blocks spelling the name "Gary" in reference to Vault 108's infamous Gary clones is in the subway car at the metro station.

Bugs

 * While removing walls after the subway track, Sonya may get struck on objects while the fighting is happening. You can walk into her in some spots to move her or reload an earlier save.
 * Trying to talk to Bobbi through the door in the miscellaneous quest 'Talk to Bobbi' wont work, so the Sole Survivor can't obtain the quest 'The Big Dig.'
 * One of the Mirelurks during the "Exterminate the Mirelurks (0/3)" part may get stuck behind the first destructible wall and be unreachable, thus making it impossible to continue the quest. Try to leave the room, talk to Bobbi, and re-enter. Alternatively, reloading an earlier save before entering The Dig will fix it.
 * After killing the guards, Bobbi and Mel will become unresponsive and the quest will not be able to be completed.
 * After pick-pocketing the guards and freeing Mel, he will become unresponsive and the quest will not be able to be completed. This can sometimes be fixed by trying multiple reloads, and waiting for Mel to leave the Security Office before the player.
 * Sometimes Mel can be made permanently aggressive to the player, making it impossible to destroy the ceiling below the Strongroom.
 * If the Sole Survivor tries to make Nick hack the terminal at some point, Sonya might get stuck and the Sole Survivor won't be able to continue the quest.
 * When breaking Mel out of the Diamond City security Office, after talking to him and leaving the building; he will reappear outside with the Sole Survivor without breaking him out.
 * Past The Dig location underground, objects may float and bounce unnaturally, especially after Sonya's blasts.
 * When trying to break the final wall, activating it will make Mel glitch and unresponsive. Shoot Mel and then talk to him to resume the quest.
 * When trying to break down the final wall, it is not able to be knocked down. Instead, talk to Bobbi No-Nose to knock it down.
 * If this does not work, using "tcl" in the console will allow you to walk through the wall. The NPCs will follow you through.
 * Alternatively, you can also use the "disable" command in the console to disable the wall.
 * Mel may disappear along with Sonya during the quest making optional walls unable to be destroyed. activating quest related walls will make them reappear.
 * When entering The Strongroom, the option to open the door may disappear, making it impossible to enter. Reloading your game from the main menu usually solves this problem.
 * After siding with Bobbi and getting paid she may suddenly become aggressive to the player (and sometimes Mel as well), this may be caused by the targetting hud power armor upgrade as retrying it with power armor unequipped allowed the quest to finish properly.
 * In the follow-up miscellaneous quest "Confront Bobbi" if you're wearing power armor with the targetting hud upgrade she may automatically become agressive as soon as you enter Hawthorne Estate. Exiting power armor before entering the estate allows you to talk to her instead of her becoming hostile.
 * When asking to break a wall, Mel will call Sonya but it will just make a quick turn and stop completely, no matter what. Saving, quitting and reloading fix this.
 * Sonya will sometimes get stuck in the ground, preventing the robot from taking any more walls down. When this happens, and the Sole Survivor activates a wall, Mel will tell Sonya to destroy the wall but nothing happens. Any interaction with Mel afterwards results in a message saying "This individual is busy." This causes the quest to not be able to be completed, and the only solution is reloading a previous save. or open the Console: click on Sonya and type: "moveto player" (if she cannot be clicked, type "prid 0011fc2e" into the console first) If this problem occurs on Xbox One save the game. Then quit to main menu and reload that save.
 * After entering the strongroom Fahrenheit and her men may automatically start attacking, forcing you to side with Bobbi as no conversation happens, this may be caused by the targetting hud power armor upgrade as this upgrade causes similar problems. As a work around, before entering the Strongroom, exit your power armor and transfer the helmet off the power armor to your inventory.
 * After entering the strongroom, Bobbi may automatically hostile, forcing the player to side with Fahrenheit and kill bobbi. Appears to be linked to having a power-armour helmet with a targeting hud. getting out of your power armour (or possibly just removing the helmet?) fixes it and allows the scene to progress normally. Leaving your power armour before entering the strongroom fixed this
 * John Hancock will ask you to "Confront Bobbi" if you sided with Bobbi No-Nose and killed Fahrenheit during The Big Dig side quest upon returning to Goodneighbor. Upon arriving at Hawthorne Estate, she will ignore the player and be non interactive, thus preventing player from obtaining Hancock as a companion.
 * Hancock might initiate his dialogue apologizing for making the Sole Survivor confront Bobbi No-Nose without having given that quest to begin with.

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