When Victor returns home to Geneva upon learning of the death of his youngest brother, William, the gates to the city are closed and he must pass the night outside the town. He notes that a storm quickly approaches, and lightning soon begins to flash around him. He perceives that a large figure creeps out from behind some trees, and he says,
A flash of lightning illuminated the object, and discovered its shape plainly to me; its gigantic stature, and the deformity of its aspect, more hideous than belongs to humanity, instantly informed me that it was the wretch, the filthy daemon, to whom I had given life. (83)
The lightning shows him the face and figure of the creature he'd made two years prior, and Victor immediately feels that this creature is his brother's murderer. Victor considers chasing the creature, but
another flash [showed that the creature was already] hanging among the rocks of the nearly perpendicular ascent of Mont Saleve [...]. He soon reached the summit, and disappeared. (84)
This creature, then, has superhuman strength and speed, as Victor sees by the lightning's illumination.
These two quotations serve to associate the creature with lightning, a symbol of Zeus, and Victor is associated with Prometheus by the book's subtitle. Zeus and Prometheus have a largely antagonistic relationship, in part because Prometheus refused Zeus information that the Olympian wanted. Victor is also in a position to refuse his creature, angering him. Ultimately, Zeus punishes Prometheus terribly by chaining him to a mountain and ordering a huge eagle to come and eat his liver every day. Victor will also be punished. This symbolism gives us some clues as to the future relationship between Victor and his creature.
Notably, when the creature first speaks to Victor, he says that, when he first came to life, "[his] soul glowed with love and humanity," but being alone and miserable has made him bitter (114). Victor responds, in part, by saying, "Cursed be the day, abhorred devil, in which you first saw light!" (115). In these references, light seems to take on a completely different meaning: it is associated, here, with goodness and life. It is not dangerous like the lightning was, but, rather, is connected to things that seem positive. This is indicative of the many different meanings associated with light and fire in the novel.