Who is Robert Walton and what is his role at the start of Frankenstein?
Walton functions as a frame story narrator whose letters to his sister begin the epistolary portion of the novel. Mary Shelley had to have someone discover Victor out on the ice. So, she created a frame story around Robert Walton. His primary function is to give audience to our frame story narrator, Victor. So, Walton is in the same position as the reader. Later, after the inner story is finished, much will hinge on Walton's decision on whether or not to continue exploring in the Arctic. What effect will Victor's warning have on Walton, on us? Is the novel itself Walton's words to us, even though the frame story is through Victor?
Walton, then, is Shelley's ideal audience: a male who abuses nature for the sake of glory. She is obviously trying to persuade such men to think differently.
Second, Walton is a foil to Victor, in that he suffers from the same hubris that pushes him to discover the unreachable realm. Whereas Victor harnesses the secret to immortality, Walton wants fame and glory for discovering the top of the world. He is also a foil in that he inhabits a land of ice, whereas Victor's discoveries are born of fire.