Flashback
Accepting a job at the remote Dry Tortugas National Park on the very edge of the Florida Keys, ranger Anna Pigeon spends her spare time--which, on the largely deserted key, is most of the time--reading letters from a long-dead relative who lived at the abandoned fort that now forms part of the park. Her peace is broken, however, by an explosion on a boat that begins to connect events described in the letters with the present, and Pigeon finds herself isolated and in danger, with storms both literal and metaphorical approaching rapidly from all sides.

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