The first character Shelley introduces to her audience is not the titular Frankenstein, but Walton, the epistolary author of the frame narrative. What is significant, thematically, is that both Walton and Frankenstein are engaged upon journeys of exploration into the unknown, which, for both of them, have become all-consuming forces. When Walton’s crew pulls Frankenstein out of the freezing waters of the North Pole, Frankenstein is evidently at the end of his journey—and it has ended in disaster. Walton recognizes a kindred spirit in him, someone who, like himself, was inspired by the stories of discovery he read as a child and whose ambition compels him to carve out a “niche in the temple” of his own. Walton is exploring the world geographically; Frankenstein is exploring the world of science, but both are men driven by powerful ambition, seeking to, as Walton puts it, “accomplish some great purpose.” Walton identifies a certain fire or spirit inside Frankenstein, feeling at once that he is the “friend” he has been seeking (something which also has echoes in the hunt of the creature for a companion, later in the story).

Walton is so entranced by Frankenstein's hopes and ambitions, so thoroughly understanding of his quest and sure that he is “immeasurable” as a man, that he does not recognize that the doctor also represents a moral lesson he himself would do well to follow. Through the character of Walton, Shelley indicates that, certainly, there is something admirable, and understandable, in the desire to push the boundaries of science, to explore the unexplored, and even to make one's own name in so doing. But she also uses Walton as an illustration that, in all areas of study, overstretching oneself can result in “peril” and entrapment. At the end of the story, Walton writes to his sister that he is surrounded by walls of ice from which there can be no escape. Later, when he sees hope of retreat, he determines that he will return to England, surrendering his ambition rather than allowing himself to be destroyed. Frankenstein, by contrast, has achieved his ambition and still been destroyed by it.