One of this year's much anticipated debut novels, Taiye Selasi's "Ghana Must Go," centers on the death of a family patriarch and the convergence of his wife and far-flung children to mourn him and attempt to make sense of their many differences. A similar plot framework is on display in Maggie O'Farrell's riveting sixth novel, "Instructions for a Heatwave," but with one crucial difference — the father figure doesn't die, he simply disappears without telling anyone.

Selasi's book was a competent study of grief and the varied outpourings it engenders; O'Farrell's is more interesting for being a puzzle. What could prompt Irish-born Robert Riordan, a happily married family man, to suddenly up and leave, empty his bank account and vanish without a trace? Mother and children join forces and piece together clues from Robert's present and shards from his past in order to track him down, but in doing so they end up uncovering just as many unwelcome truths about each other.

The events of O'Farrell's London-set novel play out over a couple of days during the summer of 1976. A record-breaking heat wave is grinding down the city's inhabitants, not least the Riordans. But when Gretta wakes one morning to discover that her husband of 40 years has gone AWOL, there is no time to feel enervated. She takes action and contacts her son, Michael Francis, who in turn touches base with his sister, Monica. The last to be summoned is errant Aoife, whom no one has seen since she left for New York three years ago. For the first time since then, all three return to their parents' home, where they conduct their investigations. But soon tensions as well as temperatures are running high. "The Irish are good in a crisis," Michael Francis explains, unaware that their reunion is causing them to unravel.

O'Farrell slides dexterously from the family's desperate paper chase to flashbacks that inform us of births, deaths and marriages, and also highlight skeletons in closets and private demons. Michael Francis' marriage is coming apart at the seams after his affair with a colleague and jealousy toward his wife's new set of friends; Monica, already with a failed marriage behind her, harbors a dark, unmentionable secret; and Aoife, while sassy and switched-on, has never dared tell anyone she is illiterate.

Rather than hang decoratively in the background, the heat wave suffuses the novel and even has a purpose. "Strange weather brings out strange behavior," we are told. O'Farrell's finely drawn characters swelter and the torrid heat "wears down their guard. They start behaving not unusually but unguardedly. They act not so much out of character but deep within it."

O'Farrell's acclaimed 2006 novel, "The Vanishing Act of Esme Lennox," also dealt with disappearance and unearthed family secrets. "Instructions for a Heatwave" re-employs such themes and tropes but deepens the mystery and jolts the reader in new ways, particularly during the book's denouement in Ireland. Once again, O'Farrell demonstrates her mastery at depicting strained relationships, skewed family loyalties and the just reachable light at the end of the tunnel.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the Daily Beast. Born in Edinburgh, he lives in Berlin.