When Ruth Rendell writes as her darkly scrutinising alter ego Barbara Vine, one has come to expect a story where penetrating character analysis goes beyond the tidy structures of the traditional crime novel and misdeeds take place in an atmosphere of moral ambiguity that owes more to Graham Greene than to Agatha Christie.

The birthday present of the title of Vine's latest book is the means whereby the charming and ambitious Tory junior minister Ivor Tesham and his glisteningly beautiful mistress, Hebe Furnal, the restless wife of a dull, devoted husband, will prolong the sexual excitement of their affair. Ivor has already marked Hebe's 28th birthday with the string of pearls that will play a threatening role in future events, but this second present involves “adventure sex”. The plan is for Hebe, bound, gagged and bogusly kidnapped, to be driven to a house in Hampstead where Ivor excitedly waits for her.

This scandalous scenario is to take place on May 18, 1990, that nervy year of IRA violence, upheavals in the Middle East and the Balkans and the shaky John Major government, whose Back to Basics campaign will be undermined, sniggeringly, by tabloid exposure of sexual and financial bad behaviour. The plan goes wrong; there is a car accident in which Hebe is killed. Although, at first, there seems to be nothing to connect Ivor with her death, those familiar with the wily procedures of this author will sense that nemesis is not to be avoided, that lives will fragment and that the pervading mood of tension will be shattered in ways that are unexpected and grim.

The story uncoils through the accounts of two bystanders: Robin (Rob) Delgado and Hebe's friend Jane. Rob, who looks back on events 17 years later, is a Pooterish financial expert, married to Ivor's sister, the much brainier Iris. Uxorious and a doting father, Rob is rather enraptured by Ivor's breathtaking amorality. Without this flamboyant chancer to shock and entertain him, his life would be charmlessly mild. Jane's involvement is told through her diaries, which Rob accommodates in his narrative. The diarist had often provided an alibi, which she did on the evening of the kidnap, so that Hebe could set out on her adventure. Jane, well-educated and intelligent, is plain and poor, living in a north London bedsit and patronised by her ghastly mother. When she loses her job as a librarian and is rejected by Hebe's widower, Gerry, hopelessness tips her into a lunatic state of despair. Always a bit of a fantasist, she becomes less able to laugh off her delusions, which are not always delusions. This bodes ill for Ivor.

Like most successful politicians, he has no self-doubts; comfortable with his lust for power and his basic instincts, he doesn't intend questioning either. Unlike the cautious Rob, he doesn't realise “how we walk all the time on that thin crust which covers terrible abysses”. He acknowledges the need for discretion, but his restless energy won't let him lie low; a disastrous act of recklessness ensures that the thin crust he walks on will, in time, snap and crumble. Jane, slovenly and mopish, is unlike the ebullient Ivor in every way except for a ruinous tendency to play with fire.

Every move this pair makes suffuses the novel with jittery expectation. It is like reading a Greek myth, only there are no supernatural portents; evil comes about because human beings, acting out of self-interest, make mistakes. And Vine's human beings are very human, down to their annoying speech patterns. Jane's controlling widowed mother rains truisms on her dejected daughter (“I've always believed you have to cut your garment according to your cloth, Jane”), while Ivor irritates Rob with expressions such as, “Oh, please. You jest.”

These wayward characters are intensely imagined and far from the usual uncomplicated stereotypes of victims and perpetrators. Following the dark tracks of their unravelling lives is an experience that is both fearful and satisfying.

The Birthday Present by Barbara Vine
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