Contemporary fiction lacks many things, but precocious children are not among them. Wherever one looks — from the work of Jonathan Safran Foer to that of Marisha Pessl — these overachievers are wielding their bloated vocabularies, quoting Heidegger, contemplating the void, and generally telling us what they — or just as likely, their authors — have been reading. Like overbearing Manhattanite parents, their creators feel obliged to subject their fictional progeny to a barrage of extracurricular activities. Such novelists — indeed, such parents — would appear to find their children not sufficiently interesting as children.

It is with some wariness, then, that we make the acquaintance of Che, the hero of Peter Carey’s lithesome and impetuous novel, “His Illegal Self” (Knopf, 288 pages, $25). Politically if not experientially savvy, this 7-year-old New Yorker, going on 8 and named after you know who, is very much aware of SDS and its splinter group Progressive Labor, but has never been to Grand Central Station and has never heard Philadelphia referred to as “Philly.”

The son of two leftist radicals wanted by the FBI, Che has been raised by his grandmother in the cloistered opulence of the Upper East Side. She calls him Jay, smoothing over the revolutionary connotations. It is 1972. Vietnam is in full swing and Watergate is just around the corner.

One day, a woman arrives. After an argument with Che’s grandmother outside Bloomingdale’s, she takes him by the hand and runs into the subway. Che believes the woman to be his mother, but she asks that he call her Dial. That night, in a Philadelphia motel room, he turns on the television and sees a photograph of himself, at which point he realizes, “Something very bad had happened.”

The pair is making its way through the back roads of Queensland, Australia, before the reader is given any clear idea of what this very bad thing may have been, exactly. “Dial,” it turns out, is Anna Xenos; she is not Che’s mother at all, but only a friend of Susan Selkirk, whom she knew during their SDS glory days, and who has been enlisted by Susan to escort Che to a clandestine meeting with his estranged mother. Things go very wrong, however, and by the end of the day, Anna is a fugitive.

Propelled in equal parts by fear, confusion, and the demands of Mr. Carey’s plot, Anna accepts some passports and a large sum of money, and flees with Che to Australia, where she purchases a dilapidated hut in a bucolic hippie commune. Che, exhilarated and bemused, is still under the impression that Dial is his mother and that they will soon be reunited with his father. The gradual winnowing of this misconception, and the strangely affecting relationship that develops between the boy and his surrogate mother, become henceforward the bright center of the book, which coyly chooses to suspend those questions — Will Che ever be reunited with his father? Will Dial be able to return to civilization? — that most engage the reader.

Children are useful to writers, in a moral as well as a technical sense, because they provide fresh purchase on the tenacious pathologies and illusions of society: A child, more easily than an adult, can say that the emperor has no clothes, or that the Fugitive Slave Act is an outrage to human dignity. Whereas Twain made Huck Finn a kind of vernacular poet, Woolf and Joyce deliberately corseted their prose in an attempt to get as close to the incongruities of a child’s inner world as possible. Mr. Carey clearly has Stephen Dedalus in mind when he has Che think, “And then no one spoke and it made the boy feel sick and worried like when you watch the Kenoza Lake stars and try to imagine the end of space. You build a brick wall but when you break through there is still more space.”

Indeed, Che has more in common with the children of Joyce and Woolf than with those of many contemporary authors, because Mr. Carey allows him his naïveties and confusions, without feeling the need to dress them up in the oversized clothes of the budding littérateur. Dial reads Jack London to him in a motel room: “He thought ‘The Call of the Wild’ must be the best book ever written.” In a coffeehouse, Dial speaks to a union organizer who she believes will help hide them from the law, while Che, freed from the dominion of Grandma Selkirk, sits by obliviously, “pouring sugar into his Coca-Cola.” Later, at the commune, young Selkirk begins to tire of his new friends, one of whom suggests they entertain themselves by digging holes, as Mr. Carey captures the endearing solipsism of childhood: “[Che] had invented digging holes and now he was sick to death of it.”

In the construction of plot and the manipulation of coincidence, Mr. Carey loves pushing the bounds of plausibility, but “His Illegal Self” succeeds because the reaction of his characters to their outrageous fortunes always remains securely tethered to the real. At one point, much to his frustration, Che is left for the day to help one of the hippies with the gardening. Before leaving, Dial asks when he would like to be picked up. “When I’m done, he said, wanting to hurt her but not wanting her to go.”

Mr. Harvey is on the editorial staff of the New York Review of Books. He last wrote for these pages on Mark Edmundson’s “The Death of Sigmund Freud.”