DAISY JOHNSON'S FIRST novel, "Everything Under," is a force of nature. Its narrative is slippery as an eel and tangled like the murky, wreckage-strewn waterways of its Oxfordshire setting. Its title, possibly by design, recalls the debut of another writer, also resident in Oxford, who went on to have a glittering career. Like Iris Murdoch's 1954 novel, "Under the Net," Johnson's Man Booker Prize finalist is concerned with language, secrets and the damage wrought by what's leftunsaid. Johnson, who at 27 became the youngest writer ever to reach the last round of the prestigious prize, also shares Murdoch's love of myth. In "Everything Under," she subverts Sophocles' "Oedipus Rex" by expanding the marginal part of Jocasta. Sarah, as she is called here, is both linchpin and catalyst for the deterministic events that follow. She is described by her "enthralled" daughter, Gretel, as "like a preacher or the leader of a cult," but also as "a runner, a giver-upper." Gretel, who works as a lexicographer updating dictionary entries, is haunted by the way her mother abandoned her when she was a teenager. And she has spent the last 16 years fruitlessly trying to track her down. Ringing up the local morgues has become a habit: "Sometimes I thought that I kept doing it to make sure you were not coming back." The novel is built around three chapter headings that are repeated over and over: "The Cottage," "The River" and "The Hunt." The first of these is an isolated home where the adult Gretel has retreated to lick her wounds; the second is where mother and daughter lived on a houseboat for several years; and the third explains both Gretel's search for her mother and a ghoulish presence on the river that she and her mother refer to as the Bonak. This monster is sometimes glimpsed - "It is double-headed, has more limbs than it must need, flings in and out of the dull pockets of candlelight" - but is also a shared symbol foreboding tragedy and loss. The supernatural is something Johnson (who was born on Halloween) already explored to electrifying effect in her story collection, "Fen," which was set amid the flooded coastal plains of eastern England. In one story, a girl goes on a hunger strike and out of empathy metamorphosizes into an eel; in another, a house becomes furiously jealous of a woman's lovers. Johnson has a way of presenting these scenarios matter-of-factly, grounding the fantastic in the earthy details of country life. In her short stories and in "Everything Under," she portrays female characters less as mothers and wives than as fully fledged characters who aren't defined by any preconceived role. Sarah's sense of her own independence, which often involves ignoring social boundaries, precludes seeing her body as "a carrier, an appendage to something else." Yet, as Gretel points out, her mother is still hoodwinked by a certain type of male refinement: "Men who liked espressos, steak tartare, white chocolate macaroons; men who enjoyed subtitled films, who wrote in the margins of books then gave them to you to read after you'd had sex in their city flats or cabins in the woods or country houses with corridors like throats leading to doors you walked in and out of." There are other doors that open in "Everything Under," leading to places where gender is fluid. The Oedipal figure in Johnson's novel is Margot, a young girl who identifies as a boy and keeps her hair cut short and her breasts tightly bound. Hence Margot becomes Marcus the runaway, keeper of a murderous secret. For a while, he finds asylum with Sarah and Gretel on board their boat. But it is a sharp-edged refuge, predicated on a private language mother and daughter have invented to share only between themselves. The water "effs" along; everything that comes down the river is some kind of "sprung"; time spent alone is "sheesh" time; and being called a "harpiedoodle" is not a compliment. "Again and again I go back to the idea that our thoughts and actions are determined by the language that lives in our minds," Gretel muses. Without their private language, she believes, the terrifying Bonak might not exist. Johnson often employs unusual juxtapositions of language or imagery: "The rental car was red and the hospital seemed to be mostly a long corridor," or "The mass of birds rose up my throat, flooded out through my cracked jaw." Her dialogue is also distinguished by a complete absence of quotation marks. But far from being enervating, this helps to carry Johnson's narrative along, allowing it to flow like a river. The setting of "Everything Under" is primordial: Gretel wants to tell her mother that "we are determined by our landscape, that our lives are decided by the hills and the rivers and the trees." Johnson digs beneath the surface of her novel's pulsating landscape. The characters themselves embody it in unusual ways. "You were the messy river," Gretel says of Sarah. "You were the pines shedding bark in summer and the ground littered with my metal traps." In a 1962 article for the British magazine The Spectator, Iris Murdoch wrote that "the mythical is not something 'extra.' We live in myth and symbol all the time." In "Everything Under," Johnson carries on this grand tradition by making something very old uncannily new. TOBIAS GREY is a critic and writer in Gloucestershire, England.