The Arrival

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

Detailed walkthrough
Talking to Chase once you arrive in Acadia, she tells you that a synth runaway was supposed to have arrived recently but hasn't shown up. She tells you 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 you his production code to persuade him to help you.

Talking to Brooks, he pretends to not know what you are talking about until you tell 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 you that 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 you down the road and following the blood trail to a house near the shore. There, you will be confronted by trappers. You can either pass a speech check (medium difficulty) and talk peacefully or kill them. Talking peacefully, they tell you that the synth came by wounded and, not wanting to pass up a meal, they ate him. They give you 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 you a reward. 3 increasingly hard speech checks can be passed to get more and more caps.