Diamond City Blues

Diamond City Blues is a quest that can be obtained in the Commonwealth in Fallout 4.

Synopsis
After the Sole Survivor witnesses Paul Pembroke's defeat at the Colonial Taphouse, poor Paul asks them for help in getting his wife back. Problem is, a simple case of helping thy neighbor leads to a much, much bigger situation...

Walkthrough

 * 1) Enter the Colonial Taphouse and watch the scene unfold. After Paul gets his face smashed in, follow him outside and talk to him.
 * 2) Agree to help him. It's possible to persuade him to pay you 80 caps in advance. Another check allows for dumping Paul and conversing with Cooke alone.
 * 3) Return to the Taphouse. Nelson Latimer will leave the inn just as Paul enters. Cooke will question whether the player is a gun hired by Pembroke, then Paul will confront Cooke.
 * 4) Paul pulls a gun on Cooke. In order to defuse the situation persuasion is needed. Otherwise, the only option is to gun Cooke down.
 * 5) Assuming the persuasion works, Cooke will promise to break off with Darcy and give Paul a way to make her stay permanently. Since his wife's a gold digger, Paul needs to get rich. And the way to do that is by screwing over Nelson Latimer's chem deal with Goodneighbor.
 * 6) Travel with Paul to the ambush spot near Back Street Apparel. Kill everyone.
 * 7) Trish will go down and be available for interrogation. She will offer the location of Marowski's chem manufacturing in exchange for her life. Killing her will produce a note that identifies the location as the Four Leaf Fishpacking Plant and give a note showing the order in which the tripwires need to be broken. Sparing her will also give the password to the computer that disables tripwires barring entry into the plant.
 * 8) Either way, Cooke will try to kill Trish. Afterwards, he will divide the spoils and leave town for good.
 * 9) Head to Four Leaf. To open the lab, either hack/access the terminal on the gantry above the entrance or trip the lasers outside: First the one near the truck, then the one by the stairwell on the southern face, the one by the large pipe by the entrance, the one mounted on the truck's hood, and finally the one near the terminal. Enter the lab to complete the quest.