It is important to note that the story features no human characters and thus the antagonist in this case is described as a concept.
The house, which is the central figure in the story, remains standing and operational after the world around it is destroyed, possibly by nuclear weapons. The inhabitants are all obliterated except for their dog that dies soon after from hunger and radiation poisoning. The house is a symbol of advanced technology. It continues to perform its duties in spite of the inhabitant’s absence. For instance, the mechanical stove continues to prepare food and the robot in the study continues to read poems. Conflict is introduced when a fire breaks out in the house. Strong winds break a tree branch that crashes through the kitchen window, spilling cleaning solvent on the stove and starting a fire. The house employs all the technology at its disposal to extinguish the fire but fails, supposedly from the lack of human intervention.
Nature emerges victorious against technology. Technology as embodied by the house and the nuclear weapons, succeed in ending man’s existence and forging on but it is forced to yield to nature’s forces. Technology in the story is portrayed as an antagonistic force while nature restores balance.