The Marowski Heist

The Marowski Heist is a side quest in Fallout 4.

Detailed walkthrough
In order to obtain this quest, the Sole Survivor must have made certain decisions during Diamond City Blues. One method of obtaining this quest is if Paul was killed in Diamond City prior to leaving for the encounter with Trish. Alternatively, Paul can be brought to the chem deal and killed by Trish and her triggermen. A third option is to choose to completely stay out of the entire plot by refusing to help Paul at the start. If Paul survives Diamond City Blues but is killed later (i.e. killing him at the request of Malcom Latimer), this quest will not appear.

The Sole Survivor will be approached by Darcy Pembroke a day later, who is investigating the disappearance of Paul. When she asks the Sole Survivor about it, they must tell her that they will help with the investigation or inform her of Paul's death without implicating themselves (if he was in the heist). Then, after a while (about a week) speak to Darcy again to obtain the photo and start this quest.

While in Diamond City after completing Diamond City Blues, Darcy gives the Sole Survivor the Marowski Heist photo. One can either show it to Marowski to tip him off that Malcom Latimer stole from him, or show it to Latimer to blackmail him.

Blackmailing Latimer

 * 1) Latimer will offer 400 caps for the photo, or 600 with a successful speech check. After handing over the photo, the quest ends.

Tipping off Marowski

 * 1) Go to Goodneighbor and show the photo to Marowski. He will give 500 caps. Alternately, if he knows about the Sole Survivor's involvement in stealing his chems, he will forgive them rather than insisting they pay restitution for the theft.
 * With a successful speech check, he can be convinced to hand over the caps before seeing the photo. If the Sole Survivor then refuses to hand over the photo, Marowski becomes hostile. If the Sole Survivor escapes Hotel Rexford, they can then sell the photo to Malcom, resulting in a total of 900 caps (1100 if the Sole Survivor passes the speech check to receive 600 caps from Malcom). Marowski and Stan Slavin will attack the Sole Survivor on sight, but can both be killed without any negative consequence.
 * 1) Marowski will ask the Sole Survivor to kill Malcom Latimer for another 300 caps (400 with a successful speech check).

Once the quest has been completed, one can return to Darcy in Diamond City and choose whether to split the caps earned from the quest with her.

Bugs

 * If the Sole Survivor does not pay the 2000 caps (1000 caps if negotiated) and kill Marowski at Latimer's request, "Pay Marowski 2000 (1000) caps" will still show under miscellaneous quests in the Pip-Boy.
 * This can be fixed with the console command.
 * Due to the complicated nature of triggering this quest, it was not expected to start the quest when Paul lives. So to allow this in such a situation, one can enter then  in the console to start the quest (this will cause the quest to appear in your quest log). Then enter  to get the photo in the Sole Survivor's inventory and the quest can go on.