The Hold Out

The Hold Out is a side quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
Start the quest by talking to Mitch in Far Harbor's bar, The Last Plank. He will ask the Sole Survivor to find his uncle and possibly bring him back to Far Harbor.

Travel to National Park Visitor's Center, beware of the mines and traps near the entrances but try not to disarm them since they will help a bit later. Once inside talk to Uncle Ken and tell him that Mitch asked to check on him. He will immediately warn of an imminent trapper attack. The Sole Survivor can use the workbench immediately afterwards, but since one probably hasn't got the chance to set up supply lines here, the existing resources are most likely insufficient for building more than a couple of machine gun turrets.

Repel the attacking trappers. Once they are dead, talk to Uncle Ken again. With some difficult charisma checks he can be persuaded to go to Far Harbor; doing so will net more reward from Mitch, but keep in mind that Uncle Ken becomes a fully-fledged settler if he stays in his home. Regardless of the result, return to Mitch for payment. If the player character didn't ask Uncle Ken to leave, he will remain in the settlement and Mitch will send two additional settlers there.