In Chapter 7 of Frankenstein, after Victor has returned from a wonderful outing on verdant hills under what he calls "a serene sky," he receives a letter from his father, Alphonse Frankenstein. In this letter, the father tells Victor that his sweet child who delighted him with his smiles and congenial ways has been murdered on the seventh of May.
On that Thursday, Alphonse, his niece, and two sons went for a walk in Plainpalais on a lovely evening. The weather was so pleasant that they continues their walk farther than usual. When dusk came, William and Ernest were not to be found as they had gone on ahead; finally, Ernest arrived, but no William. Ernest told the father that William had run and hid in their game, but he was unable to find his brother. They searched until dark; then, they returned with torches. At around five in the morning, Alphonse discovered his son, stretched on the grass, white and motionless with an indentation made by the the murderer's finger was on his neck. After carrying him home, Elizabeth begged to see William; when she examined the neck of the victim, Elizabeth exclaimed, "O God! I have murdered my darling child," and she fainted.
Later that evening, Elizabeth informs Mr. Frankenstein that William had begged her to let him wear a valuable miniature of hers that was made of his mother, and, now, this picture is gone, having probably been taken by the murderer.