The narrator is reading a book during a train journey when he is disturbed by the presence of a baby with an unusually large head and a disconcerting stare. He investigates the history of this remarkable infant, who turns out to be Victor Stott, the progeny of a marriage of convenience between a professional cricket player and an aging spinster. Following the fathers desertion, the mother and her son were given a new home by the local squire, Henry Challis, at the request of a clergyman, Percy Crashaw.
The narrator, who is a writer, is fascinated by Victor and begins a careful study of his burgeoning talents. By the time he is five years old, the boy has read through the contents of Challis library and has familiarized himself with the entire legacy of human knowledge. Victors research leads him to deny the existence of God, which so offends Crashaw that the rector attempts to have him committed to an asylum. Challis thwarts this plan and also prevents the boy from being enrolled at a primary school where Crashaw might have the opportunity to indoctrinate him.
Victor treats all other humans with contempt but begins to form a relationship with the narrator, apparently hoping that he might find a sympathetic audience for the deductions and ruminations of his advanced intelligence. Unfortunately, the English language does not contain words for the concepts he wishes to express, and the child becomes frustrated with the narrators failure to make headway. The narrator does, however, save Victor from being pestered by the only human being who is not intimidated by his hypnotic gaze: a hydrocephalic idiot.
Eventually, the narrator becomes so discomfited by his failure to keep up with Victor intellectually, and by the subtle power that the boys stare exerts on him, that he begins to avoid him. When Victor is murdered, the narrator believes that his retreat allowed the crime to be committed, but he does not know whether the perpetrator of the crime was the idiot or the clergyman.