There are a few places in Mary Shelley's Romantic novel, Frankenstein, where Victor's happiness is restored (meaning his despair is reduced/eliminated) through nature. Given that the novel is Romantic, nature plays a large role in influencing mankind.
In the opening of chapter five, readers come face to face with Vcitor's creation. Victor, horrified by his "son," immediately becomes very ill. He dreams of Elizabeth dying in his arms. His illness cannot be cured, even though he thinks that the "attentions of my friend [Henry] could have restored me to life." Curiously enough, it is nature which puts Victor on the path to recovery, not the companionship of Henry.
I perceived that the fallen leaves had disappeared, and that the young buds were shooting forth from the trees that shaded my window. It was a divine spring; and the season contributed greatly to my convalescence. I felt also sentiments of joy and affection revive in my bosom; my gloom disappeared, and in a short time I became as cheerful as before I was attacked by the fatal passion.
Later, in chapter six, the power of nature is seen again. While better than after first seeing the creature awaken, Victor's inability to return home (due to weather and lack of strength) keeps him ill. At one point, Victor receives a letter from Elizabeth telling him of Justine's coming back to the family and her desire for him to be home. In the letter, she reminds Victor of the lake and mountains near their home--which "never change." This seems to offer Victor a sense of solace. Later, after reading the letter and waiting months to return home, Victor finds the same solace in the natural scenery around him (which Elizabeth had reminded him of in her letter).
When happy, inanimate nature had the power of bestowing on me the most delightful sensations. A serene sky and verdant fields filled me with ecstasy. The present season was indeed divine; the flowers of spring bloomed in the hedges, while those of summer were already in bud.
One can see from the two previous passages that nature helps Victor out of his despair. It seems that he finds hope in the life he finds in nature. The new buds symbolize the new beginnings Victor hopes to find, once he returns home. Essentially, nature is used to illustrate the hope Victor has in a new life (away from his creature and his obsession with science).