The Great Hunt

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

Synopsis
With her time coming to a close, the Mariner wants to hunt a mythical beast: the Red Death.

Walkthrough

 * 1) Talk to the Mariner and accept the quest.
 * 2) Sail out using the boat that brought you to Far Harbor and arrive at the Red Death Island.
 * 3) Talk to the Mariner to get your reward. Then vanquish the terrible monster.
 * 4) Return to Far Harbor.