The protagonist of John Banville’s The Sea (2005) thinks of the past beating ‘inside me like a second heart’. The rhythms of Willa’s memories are similarly syncopated. In prefaces to the novel’s different sections, she reflects in lyrical detail. By now a classics scholar, she brings to her analysis awareness of the shapes of mythological stories. In her later years, she translates Ovid’s Fasti, renowned both for its witnessing of Roman culture and for its erratic accuracy. Eliza Robertson holds these analogues lightly, as provisional lenses.

Brought together by the relationship between Willa’s mother and Patrick’s father, Eugene, in a forced and jerry-built pseudo-familial space dominated by adults’ insults and drinking, the children, nine and eleven when they meet, seek escape. While Willa’s sister Joan becomes romantically involved with Patrick’s brother Kenneth, the younger siblings tread more ambivalent terrain.

The first time Willa follows Patrick, he takes an egg from a nest, sucking it and squeezing it in his fist. Willa, like the egg – its shell ‘clay green, murmured with black splashes’ – is Patrick’s fascination and toy. His question: ‘What will you do for me?’ precedes their setting sail in a sinking boat. Both question and precarious voyage set the tone for their relationship.

A jellyfish slips into the boat. Its bell sprawls ‘like an open wound, the net of stingers grazing my thigh’, until its tentacles entangle Willa’s arm. They both know that urine will deactivate the stings. Willa refuses Patrick’s offer to ‘pee on it if you want’. ‘Oh scram’, she says, not sounding like a nine-year-old, and suggesting the remembering self’s shaping of the narrative: ‘I’ve had enough of your ideas.’ But she thrills to the possibility of passing this test in her own way.

Eliza RobertsonCanadian-born Robertson has won a swag of prizes for her short fiction, including the 2013 Commonwealth Short Story Prize for ‘We Walked on Water’ and the 2017 ABR Elizabeth Jolley Prize for ‘Pheidippides’. Her collection of short stories, Wallflowers (2014), was published to international acclaim.

Demi-Gods is her first novel. Like her stories, its strengths lie in exquisite and vivid evocation. Each encounter between Patrick and Willa is saturated in sensual detail, prickling and shimmering in the dwelling place of Willa’s recollection. The most striking of Robertson’s descriptions are at once sonically and sensually rich and acutely perceptive.

The sisters grow up like trees crushed close: ‘shovelled into the same soil, competing for sun, limbs warped with forking, needles interlocked’. When he arrives at Willa’s family home, Patrick wrecks, splinters, and buries a doll’s house Willa’s father made for her mother when he designed their beach house. Willa finds her mother standing in a kimono, massaging Patrick’s back with her feet. She imagines Patrick lifted ‘in her talons like a limp trout’. Her mother applies lipstick: a ‘hook of pink the colour of her Campari’. This poetic style stands out at a moment where pared, even austere, prose is prevalent. The bravado and abundance in that risk is reminiscent of F. Scott Fitzgerald’s style. If, occasionally, a description feels overwrought, or a metaphor mixed (a sky ‘enfolding everything in sonorous blue’), it feels worth it for the daring that is more often rewarded.

On the other hand, Robertson’s eye on the emotional and erotic currents between her characters is unerringly steady. Reading Patrick and Willa’s relationship by means of contemporary pop psychology is a trap Robertson aims to avoid. While Patrick is strange and sometimes sadistic, Willa responds with a rush and charge, and with the emergence of her own ferocity and tenderness. The dynamic, or, as Willa reflects later, the imprint, is something unique they generate, and it brings Willa her most exalted moments, as well as danger and pain.

As they grow older and the sexual tension increases, it is in moments of concentrated exchange that Willa discovers her own power. As adults, she notes that he watches her ‘with a fullness I hadn’t encountered from other boys – as if he hoped to memorise the bone of my collar, the shape of my ears, the gap of fabric under my armpits. I felt important.’ Ultimately, in the power games between them, Willa conducts the charge towards an almost-catastrophic conclusion. This takes place on a boat, with Joan, Kenneth, and the sting and sag of their foundering marriage. Its recapitulation of their first boat trip provides a more thrilling and desperate stage for Willa’s power. This heady section is the centre of this acute, edgy, and captivating novel, its murky, complicated dynamics lingering like Willa’s insoluble memories.