The Arrival

The Arrival is a quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
Talking to Chase once having arrived in Acadia, she tells a synth runaway was supposed to have arrived recently but hasn't shown up. She asks the Sole Survivor to talk to Brooks, the general store trader in Far Harbor, as he is a synth and the person who meets incoming runaways first. She gives his production code to persuade him to help the player character.

Talking to Brooks, he pretends to not know what the Sole Survivor are talking about until telling him his code, at which point he begins cooperating. He explains that the synth came in frightened and ran off before Brooks could tell him where to go. He tells the synth ran off to the south of the town.

Going south, follow the marker to a pool of blood and inspect it. Markers will pop up, leading down the road and following the blood trail to a house near the shore. There, one will be confronted by trappers. One can either pass a speech check (medium difficulty) and talk peacefully or kill them. Talking peacefully, they tell the synth came by wounded and, not wanting to pass up a meal, they ate him. They give his head. Without the speech check, they will become hostile. Kill them and loot the bodies to find the synth head instead.

Return to Chase and she'll offer a reward. 3 increasingly hard speech checks can be passed to get more and more caps.