The Red House mystery

Dr. Darkham had married for money, regardless of the fact that the girl was an exceedingly vulgar and exasperating person. Now Dr. Darkham falls passionately in love with beautiful Agatha Nesbitt, who shuddered at him, and loved, and is loved by, Dr. Dillwyn. One day when Mrs. Darkham falls accidently on her head, and lays at death's door, her husband stifles her with a wet rag, and no one knows but their idiot and dumb son, whose mother has been the only affection. It takes some time for his benumbed brain to understand the crime, but then he avenges his beloved mother in a terrible manner.