The poem is an extended metaphor, with the author imagining the fog as a cat approaching on small, quiet steps, as cats do while stalking. Only a cat can move in this manner, nearly imperceptibly and completely silently. Cats use their paws to feel their way along when they cannot see what is before them. They use the tiny, sharp claws on each foot to pierce thick fur and flesh alike. When a cat stalks its prey, it does so fully aware of its surroundings and ready to strike if the need arises. Cats are very skilled hunters who know how to take down their prey efficiently and without harm. In the poem, the cat's "little cat feet" are those of a young girl. The word "feet" here refers to her small, delicate hands as well. She is coming toward him slowly but surely, like the fog, undisturbed by whatever lies beyond her reach. This poem is about fear. The poet is afraid that someone will discover his secret love affair and expose them both. He fears that she will reject him once she learns the truth about him. Even though he knows that she loves him too, he is still filled with anxiety over whether or not she will stay by his side after knowing the truth about his past behavior. Cats have long been associated with witchcraft.