1880s, Essex, England: Idealistic young doctor Simeon Lee is called from London to treat his ailing relative Parson Oliver Hawes, who lives in Turnglass House on a bleak island off the coast. Hawes believes he's being poisoned by his sister-in-law, Florence, who was declared mad years ago after killing the parson's brother in a jealous rage. Hawes keeps her locked in a glass-walled apartment in the Turnglass library; the secret to how she came to be there is found in his tête-bêche journal, where one side tells a very different story from the other.

1930s, Hollywood: Celebrated author Oliver Tooke, the governor's son, is found dead by apparent suicide. His aspiring actor friend Ken Kourian isn't so sure Oliver took his own life. He finds a link between Oliver's death and the mysterious kidnapping of Oliver's brother when they were children. He also discovers the secret incarceration of Oliver's mother, Florence, in an asylum. To get to the truth, Ken must decipher clues hidden in Oliver's final book, a tête-bêche novel called The Turnglass--which is about a young doctor named Simeon Lee . . .