Woman Without a Past - Phyllis A Whitney

From an Edgar and Agatha Award winner: A mystery writer must solve the puzzle of her past when she meets the South Carolina family she never knew existed.
 
Popular mystery novelist Molly Hunt knows all about the twists and turns of fiction, but real life has thrown her for a loop. Raised by adoptive parents on Long Island, Molly has just made a stunning discovery: She’s the daughter of South Carolina blue bloods and was kidnapped as an infant from their ancestral home in Charleston. Now, she’s heading south to solve the puzzle of her beginnings—totally unprepared for where it will end.
 
At Mountfort Hall, her birth family’s imposing plantation, Molly comes face to face with her past: her neglected twin sister; her reclusive and mentally imbalanced mother; a calculating cousin, now the Mountfort patriarch who has no tolerance for this lovely new intruder; and a resident psychic who sees into a deadly world all her own. It’s only when Molly discovers a letter from her late father that she comes to realize how much danger she’s in—and what it’ll take to escape the shadows of Mountfort Hall alive.
 
“In one of her smoothest suspense novels . . . Whitney combines a dynamic, likable heroine with eccentric characters, romantic entanglements, family ghosts and a charming setting” (Publishers Weekly). It’s everything readers expect from the “Queen of American gothics” (The New York Times).