The hero of the novel, Mr. Barnstaple, is a depressive journalist in the newspaper "The Liberal." At the beginning of the story, Mr. Barnstaple, as well as a few other Englishmen, are accidentally transported to the parallel world of Utopia. Utopia is like an advanced Earth, although it had been quite similar to Earth in the past in a period known to Utopians as the "Days of Confusion." Utopia is a utopian world: it has a utopian socialist world government, advanced science, and even pathogens have been eliminated and predators are almost tamed. Barnstaple is confounded and confused by the utopian attitudes: "where is your government ?" he asks. "our government is in our education" is the answer. Barnstaple gradually loses his Victorian English narcissism. For instance, Wells makes comments on personal responsibility when Barnstaple sees a person slaving over a rose garden at high altitude and asks, "Why don't you hire a gardener?" The answer is, "The working class has vanished from utopia years ago! He who loves the rose must then serve that rose." Barnstaple is changed by those experiences and he loses his Eurocentric view of the world and starts to really get the idea of the place. As this conversion starts to take place, Utopians begin to fall ill.
This, however, means that the newly arrived Earthlings pose a grave threat to Utopians, as the latter's immune system has become weak; and the Earthlings have to be quarantined until a solution is found. They resent this isolation and some of them plot to take over Utopia...