Special Delivery

Special Delivery is a side quest in Fallout 4.

Detailed walkthrough
Upon visiting Bunker Hill, The Third Rail in Goodneighbor or the Dugout Inn in Diamond City, Edward Deegan will approach the Sole Survivor and offer work. If the player character previously visited Parsons State Insane Asylum and killed a few of the guards, he will mention it, though he says he doesn't hold it against them. After accepting, go to Cabot House and use the intercom to gain entry, then speak with Jack Cabot and Deegan about the job. A package has gone missing near the insane asylum that's owned by the Cabot family.

Head up to the asylum and question the guard captain, she'll mention that the raiders that stole the package (containing a mysterious serum) are at the Parsons Creamery to the north. Head up there and confront them, if the player character waits on arrival, then a fight will break out between them and they'll thin their numbers.

Kill the remainder, take the serum, then return to the Cabot House. There is an option to lie to Edward Deegan with an easy persuasion check to keep the serum at the cost of a few caps of reward, or it can be turned over. The quest ends either way, automatically starting the quest Emogene Takes a Lover.