Warning: Significant plot details follow.
The narrator of the story, a somewhat naive American admirer of English novelist Mark Ambient, visits the writer at his home in Surrey. The narrator is very enthusiastic about Ambient's work, especially his latest novel Beltraffio. He meets Ambient's beautiful but chilly wife, his sickly seven-year-old son Dolcino, and his strange sister Gwendolyn. He also learns that Ambient's wife strongly dislikes her husband's novels and considers them corrupt and pagan. Dolcino eventually becomes much more ill. In order to "protect" him from what she sees as the baleful influence of his father, Ambient's wife withholds the boy's medicine. Dolcino dies, and the details of his mother's conduct are told to the narrator by Gwendolyn. The mother, grief-stricken over her role in Dolcino's final illness, dies herself after a few months. In a grimly ironic note to conclude the story, the narrator says Ambient later revealed that his wife had become partially reconciled to his novels and even read Beltraffio in the weeks before her death.