How does the multiple narrative help to frame Mary Shelley's novel Frankenstein. What are the main themes of the novel?

Walton is the indirect narrator of Frankenstein, sharing the story Victor told him with his sister.

Victor's story can only be shared through his eyes.... the personal experience and emotions are necessary to move the plot.

Impportant themes addressed in the novel include isolation, the beauty of nature, loss, and responsibilty.