The Hold Out

The Hold Out is a 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 you 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 in the entrance 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 you to check on him. He will immediately warn you of an imminent Trapper attack. You can use the workbench immediately after this, but since you probably haven't got the chance to set up supply lines here, the existing resources are probably only enough to build a couple of machine gun turrets - try to make sure that they are the Mk 7 variants before building, for the best result.

Repel the attacking trappers. Once they are dead, talk to Uncle Ken again. With some difficult persuasion checks he can be told to go to Far Harbor, doing so will net more reward from Mitch, however keep in mind that he is a usable settler if not returned. Regardless of what you do, return to Mitch for payment. If you didn't ask Uncle Ken to leave, he will remain in the settlement and Mitch will send 2 additional settlers there.