Safe Passage

Safe Passage is a quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
Talking to Captain Avery in Far Harbor, once arriving at Acadia, she tells you that she sent out a man, Howard Dunbar, to fix the fog condensers on route to their water supply, but he hasn't returned and they're running out of water. She tasks you with finding Howard and, if you find him dead, repairing the condensers yourself.

Venturing out of the town a ways and into the ruined buildings, near Beaver Creek Lanes, the player finds Howard's body surrounded by 2 Mirelurks. Killing them and looking at Howard's body, pick up the 3 Power Modules.

From here, you are given 3 waypoints, gradually further down the nearby road and up the hill. Each waypoint points to a fog condenser. Approach each one and activate it to repair it and remove the nearby fog. At the top of the hill, upon repairing the third condenser, 2 more mirelurks will spawn. Return to Captain Avery, where you can pass 3 increasingly harder speech checks to increase your caps reward.