Faber £17.99 pp400

An island that works insidious magic on its visitors; a magus mistrustful equally of his failing powers and of his daughter Miranda; an ill-begot “thing of darkness”, whom he is called upon to acknowledge his, and who turns lethal when he fails to do so: the setting into which PD James helicopters her Commander Dalgliesh for his latest case is a Shakespearian one, and, like its great model, her story is full of reflections on ageing and the painful supplanting of one generation by the next.

It is also, of course, a whodunit, but that seems almost by the by. “It hasn’t been one of our successes, Kate,” says Dalgliesh to DI Kate Miskin at the bitter end, even though they have got their murderer. James’s gifts for the evocation of landscape, for the conjuring of atmosphere, for the precise analysis of her imagined characters have always ensured that her novels had levels of interest way beyond what their plots required, but here the sense that there ’s more to the getting of wisdom than case solving is not only implied but acknowledged.

The subplots and back-stories which ensure that almost every single suspect has a possible motive for murder are conventional — of such misleading clues are detective mysteries made. But here they add up to something more than mere required mystification. The island, off the coast of Cornwall, has a history of slavery in the distant past and, more recently, of occupation and gruesome retaliation. During the second world war, three German soldiers were locked into the eponymous lighthouse and burnt alive.

The murder that Dalgliesh and his team have come to investigate is just one of several killings that form part of the extended story, but it is the only one for which justice is likely to be done. Several of the suspects are burdened with guilt, shame or anger. There is a doctor whose misdiagnosis caused a child’s death. There is an alcoholic former priest, as damaged by self-disgust as by the physical consequences of his addiction. There is a medical researcher subject to persistent death threats from animal-rights activists. One man has served a prison term for assaulting the man who raped his teenage sister and precipitated her suicide. Another was himself violently conceived. Most of the best crime fiction derives its charge from the paradoxical tension between consoling form and menacing mood; the form suggests that every crime has a punishment, every mystery a solution and every story an ending. The mood, in the hands of the best authors (and James is one of the best, not only in this genre, but in all current British fiction-writing), persistently subverts that optimism. The Lighthouse presents a world in which pain is far too pervasive to be eradicated by a single arrest.

The novel is exciting: the passage in which handsome young Sergeant Benton, an inexperienced climber, scales a cliff, thus putting his life in the hands of the surly boatman who may or may not be a mass murderer, is a terrific set-piece of suspense-filled action writing. And the plot amply delivers the expected satisfactions of an intricate puzzle adroitly solved. But these pleasures are subsidiary to those afforded by James’s sensibility, which transforms the squalor and pettiness of crime into the grandeur of desolation. James has been signalling for decades that Webster, the great voluptuary of death, is one of her literary touchstones, and she quotes him again here, along with Auden’s warning, “Those to whom evil is done / Do evil in return.”

It is young Benton, a poetry-loving policeman like his boss, who brings out Auden’s lines. The themes of superannuation and of abdication are emphatically present. There’s not only a killer at large on the island, there’s also a deadly disease in the air, and Dalgliesh spends the latter half of the investigation confined to his sickbed while the two younger officers act for him. The murderer’s victim is also nearing the end of his career, and since he ’s a novelist James can play some teasing games with that fact. Not that the unrelievedly nasty Nathan Oliver is any kind of self-portrait, but when an author in her eighties has one character say of another “He was highly regarded . . . especially the novels of his middle period”, she invites her readers to collude with her in a sourly piquant joke.

When it comes down to it, though, Dalgliesh, like his creator, effortlessly outclasses his younger rivals. For all the daring of Benton’s climb and Miskin’s equally courageous exploits, the main action takes place silently, inside the head of our half-delirious invalid hero. Dalgliesh solves the problem, and the penetrating intelligence with which he does so is as exhilarating to read about as any life-or-limb-threatening piece of physical action. For all the agreeably nervous-making gothic scenery, the swirling mists and sinister minor characters, the greatest pleasure James offers us is the spectacle, one seldom presented in fiction, of two fine minds working: one is Dalgliesh’s, the other is her own.

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