At the start​ of Flashlight, the main character, Louisa, is a stroppy ten-year-old. She’s sent to a child psychologist, Dr Brickner, on account of her misdeeds at school in California (‘defiance, disruptive behaviour, deception, peer-to-peer conflict, tardiness, truancy, larceny’), but quickly shuts him out: ‘I don’t like people asking me questions.’ He suspects that what’s troubling her is the recent death of her father, Serk, an academic on sabbatical in Japan. He drowned one evening after he and Louisa took a walk together by the sea. ‘You told people your father was kidnapped,’ Dr Brickner says. ‘I think you meant he’d been taken away from you. Stolen. Death steals the people we love.’ She denies it: ‘I never said he was kidnapped … My mother made that up.’ It’s thought that her father, a non-swimmer, slipped off the breakwater. Louisa, ‘contentious by reflex’, can’t or won’t talk about it. She’s adept at deflection. Wily, too: among the art supplies and toys in Dr Brickner’s office is a flashlight she picks up, throwing its beam on the ceiling. At the end of the session she sneaks off with it.

The upheaval caused by having to spend a year in Japan (Susan Choi also lived there for a period as a child) may be a factor in her recalcitrance. As the daughter of a white American mother and an Asian father, she’s used to feeling different, but in Japan it’s a new sort of difference: she’s stared at as a gaijin, a foreigner. Over the months, as she masters the language, she begins to feel Japanese: ‘It was as if she’d stepped into a movie and was doing so well in her role that no one else knew she was only pretending.’ All that spoils the show is her mother, Anne, who embarrasses her and whom she wishes ‘might in some painless way disappear’. She won’t discuss this with Dr Brickner. Rather than illuminate her feelings, she plays with the flashlight.

It can’t have been hard for Choi to hit on the title of her novel, which has been shortlisted for the Booker Prize. Flashlights turn up repeatedly. There’s the one Serk carries on the beach the night he disappears; the one used many years later in a séance when Louisa, having graduated from university, is sharing a quadruple bunk room in London; the one thrust in her hand when she walks through a tunnel in Paris; the ones that guards use to patrol borders. Flashlights show the way; they expose dark corners; in the right hands they’re a servant of truth, in the wrong hands a tool of oppression. The novel has a question to ask: did the drowned man really drown? The answer isn’t easy to find. All we have are omens, chief among them the ‘needle point of bright light’ Serk saw flashing from the sea a few nights before he went onto the beach, a light that he knew was more than a fishing boat.

Louisa is difficult to warm to, and she stays that way as she ages, not least in her matricidal fury. When something goes wrong, she blames her mother. It maddens her when Anne becomes unable to walk. (She’s eventually diagnosed with multiple sclerosis and Louisa refuses to push her wheelchair.) She bitches, she insults, she steals (‘Nothing existed that didn’t deserve being rescued from Anne’). When Anne dies, Louisa experiences ‘her bereavement for her mother as annoyance’. It’s brave of Choi to make her main character so dislikeable, a trick she learned from Muriel Spark. ‘The great thing about Spark,’ she said in an interview, ‘is that she frees you from that infantile desire to affirm your own goodness by identifying with characters who are good. There’s no moral centre. The girls are awful. The men are awful. Jean Brodie is terrible. And the writing is terrific.’

Not all the writing in Flashlight is terrific, but dislikeability is a thread. Louisa’s parents are no less tricky and secretive. Serk is cold, impatient and unwilling to discuss his family history with Anne: ‘That’s none of your goddam business! Who the hell are you to ask about my family?’ Although he was born in Japan, his parents are Korean, a fact he keeps from his wife and daughter. He doesn’t tell Anne when he furtively meets his sister, Soonja, in Japan and he fools Louisa, who’s with him that day, into thinking she’s an old friend. Anne has a secret too: the baby she had at nineteen with the browbeating philosopher-guru Adrian, who persuaded her to let him and his wife adopt the child (his wife was ‘thrilled to be becoming a mother’). When the child, Tobias, comes back into Anne’s life as a teenager, she won’t admit to her daughter who he is. ‘Can Louisa discern the resemblance? Anne prays she cannot.’

‘Pale, haggard, angular, beautiful’, Tobias is foisted on Anne for a day, the first time she has seen him in sixteen years, in the hope it will dissipate his recent strange behaviour. She takes him to a strawberry farm, a safe place, except for the electrified fence they’re all warned not to touch, but on which Tobias, perhaps purposely, puts his hands. The shock hurls him backwards and he’s rushed to hospital in a bad state. What looks to be evidence of Anne’s disastrous caregiving (‘Arbitrarily she birthed him, arbitrarily she’s killed him’) turns out to be a lucky break: at the hospital a growth on his brain ‘the size of a plum’ is discovered and removed, and he’s ‘once again the gentle, helpful boy he always was’. He’s a foil to Louisa, who remains hostile even when she learns that he’s her brother: ‘His very existence insulted her.’

After his recovery, Tobias becomes the novel’s hippie saviour. At eighteen, he moves to Japan and lives with Buddhist monks, bowing and smiling as he threads through the streets, beloved by the townsfolk. His interest in exotic religion highlights the failings of his mother and Serk, with their narrow secularism and incessant fretting. Anne’s anxiety is her failing body. Serk’s is that his ancestry will become known to the American university that employs him: to have parents who came from and are now back living in North Korea will tarnish him as a communist. The tensions make the marriage a battlefield. The couple hiss, snap and fight each other, leaving cuts and bruises. To Louisa, enamoured of her father, it’s clear who’s the culprit.

The novel shuttles back and forth over more than half a century: ‘The past would not be past that easily.’ Serk dies in the opening pages, but his backstory rolls on – his early years in Japan, his arrival at an American university (most of Choi’s novels have an educational setting), his marriage and parenting. His identity is shown to be complex. Seok is the name he was given by his parents; in Japan he goes by Hiroshi to help him fit in; later, in the US, he becomes Serk. Although he’s a top student, he’s rejected from the best Japanese universities because, as a Korean, he’s a ‘resident alien’. The injustice of the imperialist system politicises others but makes him only more desperate for academic success. When his parents return to Korea, ‘repatriated’ to a homeland they don’t know and are soon disappointed by, he refuses to join them (‘They were in a place so backwards it even lacked soap’) and studies at a technical college in Tokyo. Eventually he’s accepted to study electrical engineering in the US. Little or none of this is revealed to Anne. ‘I am alone in this world entire and completely!’ he tells her. The things Louisa knows about him are ‘as meagre as a pair of backgammon dice rattling in a cup’.

Choi’s first novel, The Foreign Student (1998), was about the relationship between a Korean émigré and an independent-minded American – a foretaste of Serk and Anne. Her more recent novels include the before-and-after stories of young women. In My Education (2013), it’s Regina, the starstruck student in the throes of a lesbian affair; then we encounter Regina, the successful novelist in her mid-thirties. In the resourcefully slippery Trust Exercise (2019), it’s Sarah, the teenage drama student; later we meet Sarah, the successful 30-year-old novelist. There’s the ghost of the same pattern in Flashlight: Louisa, the whip-smart damaged child; then, briefly, Louisa, the middle-aged, twice-married mother. But the novel is bolder and baggier than its predecessors, uncovering a sinister chapter in Japanese-Korean history. And the point of view we’re given isn’t just Louisa’s: Serk, Anne and Tobias share the stage.

Flashlight grew out of a short story Choi published in the New Yorker. She says she had hoped to write ‘a very lean novel with lots of evocative white space’, citing Jenny Erpenbeck’s Visitation as a model. As the plot lines develop, however, she adds new sections, notably the account of Serk’s childhood. Less pertinently there’s the widowed Anne in a ten-year relationship with the solicitous, self-deprecating Walt (‘not much less than the time she’d been married to Serk’) and a grown-up Louisa being given a hard time by British customs officials. An abstemious novel would have sacrificed those chapters and, having evolved from what Choi calls ‘disconnected bursts of writing’, Flashlight does sometimes burst at the seams. But it’s not one of those novels Kipling deplored, ‘quivering to their own power, overloaded with bars, ballrooms and insistent chromium plumbing’. Choi has never stinted on dress, décor and kitchenware, and realism is still her mainstay. In Flashlight, however, she’s willing to risk the hard-to-believe, whether it’s an implausible development (such as Louisa’s transformation from a clever clogs to a hopeless undergraduate faced with books she ‘mostly hadn’t heard of, like Persuasion’), or her premonitory dream of a tsunami.

The least dispensable episode comes when Tobias encounters the parents of a 13-year-old girl called Yumi, who went missing on her way home from school some years earlier. They’re part of a group staging a protest downtown. ‘Since 1 January 1977,’ their flyers read, ‘more than thirty Japanese citizens have gone missing without explanation from coastal towns up and down the west coast of our nation. Our government has explained each one differently. Runaways, suicide, drowning. No bodies have ever been found.’ The compassionate Tobias is bound to sympathise, all the more so when he learns of a man called Takashi who also went missing, and of a North Korean defector who reported that Japanese citizens, often fishermen, had been abducted to instruct North Korean spies in Japanese language and culture. Hit by ‘an onslaught like a freight train’, Tobias immerses himself in supporting the Families of the Disappeared Group. One day a woman turns up carrying the photograph of a missing person he recognises – her brother, she says.

From here, three-quarters of the way through the book, the plot tightens. The missing link has been found; an engrossing story, based on historical record yet no less fantastical than fiction, is out in the open. The ‘panic-driven bouts of research’ Choi became consumed by are evident in the bibliography, which lists books about what it was like to be Korean in Japan in the middle of the 20th century and what it was like to be a kidnapped Japanese person in North Korea in the 1970s and 1980s. She illustrates the first, early on, through Serk’s experiences (what Choi’s father and grandfather went through must have fed into this). To imagine the second is more of a stretch, but Choi’s depiction draws on more than books: in 2002 Kim Jong-il officially acknowledged the abduction, more than two decades earlier, of thirteen Japanese civilians. The five who survived were then returned to Japan. The number of those taken is probably far higher.

Tobias may be the news-bearer but Louisa is the more deeply affected: she’s ‘turned into some heretofore-unknown’ version of herself and the final pages show her in a tender light, freed from her ‘reflexive hostility’. She also accesses buried memories that ‘many therapies’ have failed to unearth. It’s not a triumphant resolution, because it happens on a hospital ward. But what Choi captures so well, even as she pushes the novel to its limits (political documentation vying with fictional fluency), is what it’s like to live between two worlds. None of the characters ever quite belongs, Serk least of all.