Plot
In 1969, "the manager of Western Auto", Chase Andrews is found dead in the mud, at the bottom of a 63 ft tall metal fire tower from which he had fallen. The muddy bog floods at high tide, destroying any tracks from the killer and no fingerprints are found in the tower. A rare shell necklace, which he had been wearing on the evening of his death, is missing from his body. Local pariah and marsh ecology author "Kya" Clark, is charged with first-degree murder and condemned by the provincial townspeople. Retired, local attorney Tom Milton visits Kya and hears her story in preparation to represent her.
Kya's childhood begins in a North Carolina swamp shack with her four siblings in 1953. As their abusive alcoholic father gambles their money away, Kya's mother and older siblings flee one by one, leaving Kya alone with him until he too abandons her at the age of seven. She survives by selling mussels at Barkley Cove's general store, owned by Mabel and "Jumpin" Madison, who become Kya's de facto guardians. The townspeople revile her as the "marsh girl" and she is ostracized by the other children in the town.
Over the years, Kya's slightly older friend Tate Walker lends her books and teaches her to read and write, while Mabel teaches her to count. Tate shares an interest in marsh ecology, especially avian feathers, and begin a romantic relationship until Tate leaves for college and fails to return as promised on the 4th of July.
Five years later (in 1968), Kya begins a relationship with Chase Andrews, "the best quarterback Barkley Cove ever seen" according to deputy Purdue; he promises her marriage. Chase gives Kya a small, non-indigenous shell which she makes into a necklace and then gives back to him, after he curtly takes her virginity. Not wanting to lose the house to a developer, Kya has her marsh shells drawings and paintings published, to raise the $800 needed to pay the back-taxes on the family home.
In 1969, Tate returns to Barkley Cove wanting to rekindle their romance, but Kya is ambiguous. She ends her relationship with Chase when she discovers he is already engaged to another town girl.
Kya's older brother Jodie returns as a United States Army soldier. Their mother has died of leukemia, while living with her sister; and he has no knowledge of their three older siblings. Jodie asks to visit when he can.
Kya rebuffs Chase's persistent attentions and successfully fights off his rape attempt, vowing to kill him if he returns. The threat is overheard by a local fisherman. Chase returns and vandalizes Kya's home while she hides in the marsh. The constant threat of violence reminds her of her past with her father and leads to anxiety.
Back in the present, Kya's trial has begun. Despite knowing Kya had been meeting with a book publisher in Greenville at the time, the police and the prosecutor speculate she could have disguised herself and made an overnight round-trip bus ride to Barkley Cove, lured Chase to the fire tower and killed him. With only the speculative theory, the missing necklace, red wool cap fibers, and the fisherman's testimony, Kya is found not guilty.
Reconciled, Kya and Tate reunite, agree to a common law marriage "like the geese". Over the years, Kya publishes three more illustrated marsh ecology books, on swamp insects, sea birds and mushrooms. They are frequently visited by Jodie and his family. She offers condolences to Mabel at Jumpin's funeral. While boating through the swamp in her 70s, she imagines herself as a child seeing her mother returning to the cabin. Tate finds Kya lying dead in the boat at their dock.
Boxing up Kya's things, Tate finds a passage in her journal saying that to protect the prey, sometimes the predator has to be killed. It is accompanied by a drawing of Chase. In a hidden compartment in the book, Tate finds the missing shell necklace, which he throws into the marsh waters.
