The Gilded Grasshopper

The Gilded Grasshopper is a quest in Fallout 4.

Quick walkthrough

 * 1) Pick up the Marty Bullfinch file in Nick Valentine's agency. (Optional)
 * 2) Go to Faneuil Hall and find the gilded grasshopper on the roof.
 * 3) Read the note in it, then find the grave just west of Pickman Gallery
 * 4) Dig up the grave and claim the spoils (a shovel is not required)

Detailed walkthrough
After you read the files about Marty Bullfinch in Nick Valentine's office you can get the mission of retrieving him as a missing person. Going to Faneuil Hall and killing all the supermutants, at least 16, in the basement and on the first floor lead to the roof where you can find the dead body of Marty Bullfinch near a round table and the Gilded Grasshopper on the top of a golden couple. Reading the note attached to it leads to a grave near Pickman Gallery containing a skeleton, a legendary sword, one Gold bar, two silver bars and three copper bars.