Diamond City Blues

Diamond City Blues is a side quest in Fallout 4.

Detailed walkthrough
The quest starts in Diamond City where the Sole Survivor 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:

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

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 Paul and the Sole Survivor directly about it. 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 Paul in the bar
If the player character claims they're not with Paul, he will say "thanks for nothing" and one 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 one decides 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 the Sole Survivor 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 Cooke to stop seeing Darcy. If successful, he will no longer allow her in the bar and will tell the Sole Survivor about the chem deal. If failed, or choosing the non-Charisma dialogue, he will turn hostile. Whether one kills Cooke and reads the note or keeps him alive, it is still possible to include Pembroke in the ambush by telling him about it when reporting back to him.

Ambushing the deal

 * 1) Go north to the quest marker, just outside of Back Street Apparel. If one has a companion that is not Strong, X6-88, Cait or Dogmeat they 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 other companions (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 are a few speech checks the Survivor must pass. She will also hand over the security password, which is needed to access the chem lab's tripwire terminal. If the Survivor doesn't let her go, or does not pass the speech checks, they will not receive Trish's note and won't know how to enter the chem lab. Alternatively, the Survivor can kill her and take it 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 is decided, even if one persuades 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, the player character will need to decide how to split the goods. If one agrees to a 50-50 split, he will take all the chems and set himself up as the new owner of the Colonial Taphouse, effectively replacing Cooke as its merchant. A 70-30 split via an easy Persuade check, or taking everything (and sending him home without him turning hostile, which requires a 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. One 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 feral ghouls as the Sole Survivor approaches and of the tripwires around the building. Climb to the top and head towards the terminal on the side to gain access to the lab. If one does not have Rank 3 of the Hacker perk, they 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.
 * 30 of each if Nelson is left alive and splitting 50-50.
 * Paul Pembroke as a merchant, if splitting 50-50 with him (sells alcohol).

Companion affinity

 * Piper likes refusing to help Paul Pembroke. Also, if Piper comes with the player character to confront Cooke and they choose nonviolent options, she will give some unique dialogue. In addition, peaceful dialogue increases affinity with her.
 * Codsworth loves it when the Sole Survivor uses the speech check which states that 'No one needs to get shot' to talk down Paul.
 * Deacon likes agreeing to go with Paul, and also likes telling Paul to put the gun away when confronting Cooke. He also likes splitting 50/50 with Paul after ambushing the deal.
 * MacCready and Cait like it if the Sole Survivor gives Paul the 50/50 split.
 * Valentine hates killing Paul Pembroke to take the chems after a 50/50 split.
 * X6-88 likes it when the Sole Survivor tells Paul to kill Cooke. He also likes it if the Sole Survivor tells Trish they will definitely kill her if she doesn't give up the password. Valentine hates this.
 * Hancock and Codsworth dislike it if the Sole Survivor tells her they will definitely kill Trish if she doesn't give up the password.
 * Hancock, Cait, MacCready and Strong will approve if the player character encourages Paul to shoot Cooke.
 * MacCready dislikes talking Paul down when confronting Cooke. However, if the player doesn't take the quest, by telling Paul to "solve his own problems" when he approaches the player in the market, MacCready will say "That's just as well. Last time I got in the middle of something like this, I think three people died." alluding to one of the outcomes of the quest, although no change in affinity will occur.
 * If MacCready is present while Trish is killed, it will cause him to leave or go hostile unless his relationship with the Sole Survivor is already maxed.
 * Curie likes convincing Paul to calm down when confronting Cooke. If the Sole Survivor starts shooting at the drug deal without talking first or kills Cooke afterwards, she will hate it and leave. She likes it if the Sole Survivor gives Paul the 50/50 split.

Bugs
Blues de Diamond City Blues de Diamond City Блюз Даймонд-сити Блюз Даймонд-сіті 鑽石城藍調