The Secret of the Sands

This is a mystery novel that tells the story of the Amory family; Sir Horace Amory, his daughter Vera, his son Dick, and the wife of his late uncle, Maria. Horace had inherited the title and property "Oversand" from his deceased uncle. Maria comes to stay at Oversand hiding a secret she kept rigidly to herself. When she wanders away from the house, she is found sitting, staring intently into those boiling, shifting grey sands, from which nothing ever emerged alive that had been engulfed in their lethal coils. What is the mystery story about the shifting grey sand? Will Lady Maria Amory finally disclose the secret?