Final answer:
Victor Frankenstein withholds the truth about the creature and the murderer from his family due to fear of being labeled a criminal, his own guilt, and the terror of facing the societal consequences of his scientific endeavors.
Step-by-step explanation:
In Mary Shelley's Frankenstein, Victor Frankenstein refrains from telling his family the truth about the creature he created and the murderer because he fears the monstrous nature of his creation will be incomprehensible to them. He dreads being perceived as an assassin or a criminal if the truth were to come out.
Moreover, Victor struggles with a sense of personal responsibility and guilt, as he realizes that he is to blame for the deaths caused by the creature. Victor's own conscience and the societal implications of his actions trap him in isolation, prompting him to withhold the truth.
Furthermore, Victor's fear and dismay at the real-life implications of his scientific pursuits render him unable to face the consequences of his own actions.