Diamond City Blues

Diamond City Blues is a side quest in Fallout 4.

Detailed walkthrough
The quest starts in Diamond City where the player character must help Paul Pembroke deal with Henry Cooke, the barkeeper of The Colonial Taphouse, and then intercept a drug deal in order to gain access to a chem lab. The quest is obtained by witnessing Pembroke get in a fight with Cooke over Pembroke's wife. The fight happens when the player character enters The Colonial Taphouse in Diamond City for the first time. Shortly after the scene Paul Pembroke will seek out the player character in Diamond City and the actual quest starts.


 * 1) Visit the Colonial Taphouse and watch Paul Pembroke get beaten by Henry Cooke.
 * 2) Wait until later and talk to Paul around town to get the quest.
 * 3) (Optional) Demand payment with a speech check.
 * 4) (Optional) Make Paul stay behind and confront Cooke alone.
 * 5) Follow Paul (or go alone) to the Colonial Taphouse to confront Cooke.
 * 6) At this point the quest takes one of a few different turns, which will determine who is present when ambushing an upcoming chem deal:

Option 1: Confront Cooke with Paul
Paul pulls a gun and things escalate quickly. Either calm him down with one of three easy Charisma checks, or encourage him to attack Cooke. Taking the former ensures that both Pembroke and Cooke will be part of the upcoming chem deal ambush, as Cooke tells both of you directly. Taking the latter leads to Cooke's death. The Sole Survivor can get Cooke's note from his body in lieu of hearing about the chem deal directly from him. After reading the note, it is possible to either discuss the deal with Pembroke and enlist him as backup, or to cut him out entirely by not mentioning it.

Option 2: Kill Pembroke in the bar
If you claim you're not with Paul, he will say "thanks for nothing" and you will not be able to persuade him when he draws his weapon. He and Cooke will open fire on one another, but neither will be hostile, presenting an opportunity to side with one by firing on the other. If you decide to help Cooke (or let him kill Pembroke, very likely to happen as he has a stronger weapon and is a higher level), the quest proceeds with Cooke telling you (and only you) about the deal. If Cooke dies, the quest reverts to Option 1.

Option 3: Confront Cooke alone
This requires passing a medium Charisma check during the initial conversation with Paul. There is a choice between a medium Charisma check and two easy Charisma checks to get him to stop seeing Darcy. If successful, he will no longer allow her in the bar and will tell you about the chem deal. If failed, or choosing the non Charisma dialogue, he will turn hostile.

Whether you kill Cooke and read the note or keep him alive, it is still possible to include Pembroke in the ambush by telling him about it when you report back to him.

However the bar scene plays out, you can either end up going to the chem deal solo, with Cooke, with Pembroke, or with both.

Ambushing the deal

 * 1) Go north to quest marker, just outside of Back Street Apparel. If you have a companion with you that is not Strong or X6-88, you MUST converse with Nelson Latimer and Trish before attacking them in any way. They are not considered hostile until combat begins, so any harmful action against any of them will be seen as "murdering a non-hostile" by your companion (and counted as murder in the Pip-Boy's crime statistics).  This is risky on higher difficulties as the five hostiles immediately open fire from five directions, with little chance to get behind cover.
 * 2) Once everyone else is dead, the Sole Survivor can interrogate Trish, there's a few speech checks the Sole Survivor can make for extra XP, but it's not hard to get her to give up the details on the chem lab.  Alternately can kill her and take Trish's note off her body.
 * 3) The outcome of the ambush changes depending on who is still alive after the attack:
 * If Cooke is present at the ambush and still alive, he will attack Trish regardless of what you decide, even if you persuade her to give up the password. It is possible, however unlikely, that Trish will gain the upper hand in the fight (by retreating far enough away that his shotgun will miss and/or picking up a better weapon from a dead Triggerman) and kill Cooke.
 * If Paul is present at the ambush, you will need to decide how to split the goods. If you agree to a 50-50 split, he will take all the chems, set himself up as the new owner of the Colonial Taphouse (effectively replacing Cooke as its merchant).  A 70-30 split (easy Persuade check), or taking everything (and sending him home without him turning hostile, which requires hard Charisma check), will result in him staying in his original residence, and he will speak negatively to the Sole Survivor from this point on.  You can also kill him and take everything, but Cooke will become hostile if he is alive and hasn't moved far enough away.

Afterwards, Cooke will either be dead or leave Diamond City for good, thus he will no longer be available as a merchant. The quest continues, alone, to Marowski's chem lab.

Chem lab

 * Head to Four Leaf fishpacking plant on the East coast, being wary of the ghouls as the Sole Survivor approaches, and of the tripwires around the building. Climb to the top and make your way to the terminal on the side to gain access to the lab. If you do not have Rank 3 Hacker you can access the Chem lab by triggering the tripwires in the order depicted in Trish's note.
 * Once the Sole Survivor gains access the quest is considered complete.

Rewards

 * 800-1000 caps looted from Nelson Latimer, if killed
 * Up to 60 each of Buffout, Jet, Psycho, and Mentats, if not splitting 50-50 with Paul
 * Paul Pembroke as a merchant, if splitting 50-50 with him (sells alcohol)

Bugs

 * Wearing Power Armor with the targeting HUD mod will result in Paul pulling the gun out and starting a gunfight until one of the contendents is dead. Exiting the suit before the fist fight starts allows the scripted fight to end and the quest to continue.
 * If you stand at the entrance to the counter of the bar before Cook leaves to fight Paul and proceed to block his path, the fight will continue to loop until Paul is dead, keeping the quest from proceeding to the next stage.
 * If Paul Pembroke is present during the drug deal, he will remain stuck there when taking the drugs if you chose the 50\50 speech choice. If the player returns to the drug deal after a fast travel, Paul will have new clothes but will still stand there. Eventually, he will get shot by raiders or vanish. Speaking to Colette will show dialog option as the quest was never completed, currently there are no work around to fix this issues.
 * If you decided to go without Paul Pembroke, and didn't speak to him before the drug deal, after the deal he will head towards the site, and he will remain stuck there with no speech choice. The quest to "Report to Paul Pembroke" will remain in your Pip-Boy.
 * After the quest is completed, there is a possibility that Cooke's note will remain in your inventory. If playing on PC, you can use the console command to remove the note.
 * If you left the Colonial Taphouse without searching Henry Cooke's body, there is a possibility that is body goes missing but the quest marker will still appear behind the bar. Playing on PC, you can use the console command to add the note and . This will update the quest log.
 * The dead bodies of Nelson Latimer and the Triggermen have their inventory repopulate over time, creating an endless loop of caps, clothing, and weapons.
 * When entering the chem lab at the Four Leaf fishpacking plant with Nick Valentine as a follower, he may behave as if critically injured the entire time the player is in the room. Exiting the building will cause him to revert to normal behavior.

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