In the distant future, humans have colonized Mars and live an apparently easy life, supported by efficient and intelligent robots.
Like many other human adults, he suffers from progressive agoraphobia, which becomes extreme after his only son departs to spend time on Mars.
Before he can begin this project, he learns that Juwain, a Martian friend and brilliant philosopher, has contracted a terrible disease that only he can cure.
Senior political figures make clear that Juwain's death would be a tragedy for which humankind would suffer for thousands of years, and Webster is pained by the thought of forsaking his friend.
With great effort he packs for the trip, only to discover, in the last lines of the story, that the robot Jenkins, not understanding the stakes, had dismissed the spaceship that had arrived to transport Webster to Mars.