Olympia Avery was born on the Island, but left it in the past for a prolonged period of time, only returning to Far Harbor 10 or 11 years ago. At some point, she received a letter from Danny, a family member, in which he states that "ma has passed" and asks her to "come home" to their family's homestead.
She has been a permanent resident of Far Harbor since approximately 2279., eventually becoming captain of the Harbormen. She is accepted among her peers, and Mitch points out her moral superiority by calling her "holier than thou," albeit in a slightly mocking tone.
As the leader of Far Harbor, Avery is involved in the increasing conflict on the Island, attempting to keep the peace with both Acadia and the Children of Atom to the best of her ability, even though her attempts to resolve conflicts peacefully are frequently hampered by Allen Lee's hostility towards everyone who is not part of the Harbormen.
However, unbeknownst to everyone involved, at some point in the past Captain Avery was murdered by DiMA and replaced by a synth. This was done by DiMA in an attempt to infiltrate Far Harbor and to protect his people, and the remains of the real Captain Avery, alongside her locket, are located in the basement of the Vim! Pop factory. When confronted by the Sole Survivor about her being a synth, Avery initially reacts shocked and with denial, but starts to accept reality after listening to the holotapes.
↑Sole Survivor: "What's your beef with Avery?" Mitch: "Avery was born on the island, but she left for a good long spell. Didn't come back until, well, ten? Eleven years ago? And since then she's been trying to make us adopt all sorts of mainland nonsense. I ain't arguing she doesn't do good or her heart being in the right place, but why change what ain't broke." (Mitch's dialogue)
↑Sole Survivor: "You've lost the whole island?" Captain Avery: " The Fog's been here forever. There are good years when it recedes and the island's almost normal.Then there are times where it spreads all over. And people have to cling to any patch of land free of the Fog.For the past... oh, eight years or so, it's been getting... as bad as it's ever been.Now, Far Harbor's one of the only places left that's safe." (Captain Avery's dialogue)
↑Mitch: "I fear we had you all wrong." Debby: "Well, Captain Avery didn't." Mitch: "Right, holier than thou Avery got the right of it. And thanks for reminding me. *sigh*" (Mitch and Debby's dialogue)
↑Sole Survivor: "Aren't you saying that just to protect yourself?" Captain Avery: " I've dedicated my life to trying to keep this rust bucket of an island in one piece.And I'll be damned if this changes anything." (Captain Avery's dialogue)
↑Allen Lee: " I wasn't expecting nobody. Next shipment's three days out.Wait. That's not one of mine." Captain Avery: "Jesus. Ease up, Allen. We got visitors." Allen Lee: "Mainlanders ain't nothing but trouble." Captain Avery: "Put the damned gun down." (Allen Lee and Captain Avery's dialogue)
↑Sole Survivor: "I have proof that DiMA killed the original Captain Avery. Here." Captain Avery: "I... But that's... My locket. It was lost in a fire.And... the skull. It can't be...Listen, I'm me. I remember everything.I can't be... a synth. You're wrong." (Captain Avery's dialogue)
↑Sole Survivor:"These holotapes prove it. Listen." Captain Avery: "They're fake... They're... Oh god.It's true, isn't it? I'm a synth. Do you have any idea what it's like?To learn everything you know, everything you believe... is a lie?" (Captain Avery's dialogue)
↑Sole Survivor: "No, I'm not an investigator." Pearl: "Oh drat. You look just like the person that Mayor Avery had described. I was sure you were the one investigating that missing persons case." (Pearl's dialogue)