Mayor Hancock wants to know what the deal is with Pickman Gallery and why the raiders go awfully quiet whenever the subject is brought up. The Sole Survivor can take the job.
The player has to talk to Hancock once at Goodneighbor and accept the job to scope out the Gallery. They can haggle the price up to 250, 300, or as much as 400 caps. Then they simply have to enter the Gallery and retrieve Message to Jack from the marked dead body and return to Hancock with evidence of what's going on at the gallery.