We are introduced to Robert Walton, a 28-year-old sea captain who is embarking on a journey to the North Pole region in order to find a passage from the Pacific to the Atlantic. He writes the letters to his sister, Mrs. Saville, in London, England. He has talked about making this expedition for six years: it has been a favorite dream of his, and he is pleased that he finally has a chance to make good on his promise to himself. Other dreams, such as becoming a poet or a playwright, have not worked out. Therefore, this vision must succeed. The writer of letters is thrilled that he will satisfy an "ardent curiosity" by setting foot on a part of the world never visited by man. As he prepares for voyage by taking practice trips in the North Sea of Russia, he is worried that he has no friend on the trip who will be able to sustain his disappointment should the dream not work out. He admits this is a romantic, emotional need, but it is there. Unfortunately he does not connect at all with the other men, even though he is very fond of his lieutenant and the ship's master. He is nevertheless extremely excited for his journey.
Once actually on the voyage, things are going well. But a strange thing happens. In the middle of the ocean, on sheets of ice, they spy a sleigh pulled by dogs with a large figure driving. He disappears, leaving the entire crew in puzzled wonderment. The next day, another sleigh is at the side of the ship, on the brink of destruction amidst the ice. This time, however, there is a regular-sized human there, asking to where the ship is bound. He boards the ship, nearly frozen and completely fatigued. When he is a bit recovered, Walton asks what he is doing up here. The stranger says he was tracking someone who fled from him. Apparently, it was the large figure Walton and his men saw earlier. Walton begins to spend time with the stranger. He is morosely unhappy, and when Walton talks about how he might be sacrificing his life on this expedition for the sake of knowledge, the stranger breaks down and decides to tell him the tale he has kept secret in order to reverse that opinion.
The structure of the book is arranged: we know that the unnamed stranger will be the general narrator, and Walton, substituting for all readers, will be the audience to whom he speaks. Shelley is setting up a number of themes in this clever kind of introduction. Walton's intense desire for discovery and the unknown, to the point that he would risk his life at sea, molds him along the lines of the epic hero type. Diction such as "glorious" and "magnificent" is used to describe his mission. Walton is consumed by the need to be immortal by doing what has never been done previously. He suffers from hubris and believes that he is invincible, destined to complete this dangerous journey. That this ultra-confident attitude upsets the stranger so much (he likens Walton's curiosity to drinking from a poisonous cup) is telling. The stranger believes that the quest for new knowledge can lead to self-destruction. While the idea sounds strange, it is a key theme to remember.
Walton's undertaking of this journey is a comment upon the larger society as well as upon his character: it is the outside world that is constantly urging its members to leap tall boundaries, that they might gain recognition and fame. Walton's values are definitely questionable. It does not seem that he really belongs on this mission, with so little experience, but he refuses to let this dream go. He is highly motivated and in his prime, a younger version of the weathered stranger, who had the same ideals at one point but has had to relinquish them. That Walton complains of not having peers to whom he can relate illustrates the most basic human need of companionship. Anything with an iota of humanness feels such a compulsion for friendship and emotional ties; anybody would be justified in going great lengths to find these things.