Victor Frankenstein was rescued by Robert Walton and was in the process of telling him about his misfortunes and how he ended up in one of the remotest part of the world. He also urged his listener not to follow in his path but to learn from him the dangers that were present when one attempted to be greater than it was naturally possible (for him to play the role of God).
Victor told of how he came to acquire the ability to bestow life on a lifeless body and his interest to actually create life. He however did not elaborate the process towards achievement of the feat because of the “dangers of such knowledge”. Through his story, he explained how acquisition of that knowledge changed his life negatively and how it directly affected those he loved. His knowledge led to the creation of the monster that eventually killed Henry, William, Elizabeth and by extension, Justine. From the start, his knowledge only caused him grief, he not only suffered physically but he was also detached from his family and social life. His creation took most of his time and he was completely obsessed with the process and the knowledge.
Victor described the dangers of the knowledge as the events that followed after creation of the monster and the impact it had not only on him but his immediate family.
I do not think that the pursuit of knowledge is an exception to this rule. If the study to which you apply yourself has a tendency to weaken your affections, and to destroy your taste for those simple pleasures in which no alloy can possibly mix, then that study is certainly unlawful, that is to say, not befitting the human mind.