Victor receives a letter from his father telling him to return home immediately. William, the youngest in the family, has been murdered by strangulation. The family were out on an evening stroll near their home when the young boy ran ahead of the group. He was later found "stretched on the grass livid and motionless; the print of the murder's finger was on his neck." Missing was a locket that Elizabeth had given William of their mother.
When Victor arrives at the city gates, they are closed, so he must remain outside the city in Secheron until the gates are reopened at dawn. It is at this time that he realizes that he had been gone six years from home and that two years have passed since the creation of his monster.
While near Secheron, on Mont Blanc, Victor catches a glimpse of the monster between flashes of lightning. Having a nagging feeling that the murder of his little brother could be the handiwork of his monster, Victor questions, "Could he be (I shuddered at the conception) the murderer of my brother?" The monster disappears when he realizes that he has been seen by his creator. Now fully believing that his creation murdered William, Victor knows that he cannot reveal the source of the crime without some serious inquiry about his creation. Thus, Victor is torn between revealing the monster and risking inquisition on his past or letting the criminal justice system free the accused.
Finally at home, Victor engages in a conversation with his family. He learns that Justine is accused of the murder with circumstantial evidence. He relays his assertion of Justine's innocence and states that she will be found not guilty. His words reassure Elizabeth in a time of great need.
Victor receives a letter from his father telling him to return home immediately because William, Victor's youngest brother, has been murdered by strangulation. The significance of the letter is that it is a turning point in the book, in which the monster now has a real presence in the story; he is a threat to his creator. Up to this point, the monster has been in the back of Victor's mind. Here the monster is asserting himself into Victor's life.
The setting and atmosphere sets the stage for Victor to see the monster. The reader expects something to happen because of how Mary Shelley describes the scene. Also, it is interesting that lightning has such a recurring role in the story. It is first how Victor learns about electricity and gains an interest in natural sciences. Then, it is assumed that he uses electricity to "jumpstart" his creation's life.
Not only does Victor know that the monster is responsible for the death of his brother (psychic communication), but the monster was able to find Victor's family (via psychic communication). Psychic communication is a Gothic novel quality.
It is at this point that Victor realizes that creation is responsible for the murder of his brother. He cannot reveal the source of the crime without some serious inquiry about his creation of the being. Thus, Victor is on the horns of a great dilemma. The family must put their faith in the criminal justice system to exonerate the accused.
When Victor repeats his assertion of Justine's innocence, her father remarks, "She is to be tried today, and I hope, I sincerely hope, that she will be acquitted." Justine is already a martyr, in the Frankenstein family's eyes, in that she is willing to suffer the guilt for a crime she did not commit. Perhaps Shelley is making a subtle point about the criminal justice system in England during her time. The rights that are enjoyed today are not the same rights enjoyed in the late 1700s. This passage plays a commentary about the rights of the accused and poor in English society, which is obviously a concern of Shelley's mother and probably a concern of her own.