After completing Diamond City Blues, Darcy Pembroke will approach the player and give the player the Marowski Heist Photo. You have two options from hereon: show the photo to Marowski or show the photo to Latimer to blackmail him.
You can find him to Hotel Rexford in Goodneighbor. Marowski awards the player with 500 caps for the photo. If the player refuses to hand over the photo, he may become hostile. If the player hands over the photo, Marowski will ask the player to assassinate Latimer for 300 caps. This amount can be increased by a successful speech check.
When shown the photo, Latimer may offer 400 caps. You can raise the amount to 600 caps after a successful speech check. After giving the photo, the quest ends.