The Dreyfus Affair, the furore caused by a miscarriage of justice in France in 1894, is a source of perennial interest. It raises questions of national identity, political morality and personal integrity that are still relevant today with immigration, Euroscepticism and dodgy dossiers. It is also, as Emile Zola recognised, a gripping story: ‘What a poignant drama, and what superb characters.’ Like Zola, Robert Harris has recognised the Affair’s dramatic potential and re-tells it here as the taut, first-person, present-tense narrative of the heroic Colonel Georges Picquart.

Picquart was a high-flying young officer from Alsace who acted as observer for the Minister of War, General Mercier, during the court martial held in camera of the Jewish officer, Alfred Dreyfus, charged with passing secrets to the Germans. The chief evidence against Dreyfus was the similarity of his handwriting to that on an incriminating document— the bordereau — filched from the wastepaper basket of the German military attaché by the embassy’s cleaning lady. Dreyfus was duly convicted and sentenced to life imprisonment on Devil’s Island.

A year or so later, Picquart was made head of the French secret service, the euphemistically named ‘Statistical Section’ of the army’s Second Bureau. Soon after his appointment there comes from the same wastepaper basket fragments of an unsent letter-telegram which, when pieced together, reveal an ongoing traffic in secret documents. The name and address of the proposed recipient, a Major Esterhazy, are on the form.

In due course, Picquart discovers that the handwriting of Major Esterhazy is identical to that of the bordereau that incriminated Dreyfus. He reports his discovery to his superiors. They tell him to bury it. If Esterhazy is guilty, then Dreyfus is innocent, and to admit a miscarriage of justice in the case of Dreyfus will do irreparable harm to the army in critical times. Picquart protests against this sacrifice of an innocent man. ‘Really.’ he is told, ‘when all is said and done, what does it matter to you if one Jew stays on Devil’s Island?’

Those familiar with the Dreyfus Affair will be greatly impressed by the skill with which Harris weaves historical facts into his fictional narrative. He tells us that he has been ‘obliged…to invent many personal details’, and even for Dreyfus cognoscenti it is not always clear what is fact and what is fiction. Was Picquart, who came from a Catholic family, always so anti-Catholic? Why did he admire General Mercier for his refusal to attend mass when the governments at the time were virulently anti-clerical? Had Picquart’s affair with Pauline Monnier, the wife of an official in the Foreign Office, really been going on for 25 years? Or are we told this to scotch the rumours that Picquart was bisexual?

‘Thrillers,’ Picquart informs us, ‘may sometimes contain more truths than all Monsieur Zola’s social realism put together.’ An Officer and a Spy is more than a thriller but inevitably such a taut narrative fails to convey why the turmoil caused by the Dreyfus Affair brought France to the brink of civil war. But what we lose in in-depth understanding, we gain in excitement, as the spy becomes spied upon, the investigator becomes the suspect, and the full force of the state’s sinister apparatus of espionage and dirty tricks is directed against its own chief.

Harris’s evocation of fin-de-siècle Paris is superb, and so too are his deft sketches of people — the vain generals and the complex but crucial Major Henry. Less convincing, in my view, is his depiction of Henry’s buffoonish fellow-conspirator, Major Du Paty de Clam. Would the person who said of Dreyfus that ‘a man who betrayed his wife is quite capable of betraying his country’ have made a pass at Lucie Dreyfus when he searched her apartment? At times it seems that Harris has been swept up by Dreyfusard polemic:  even Du Paty’s breath smells of decay ‘that comes from deep within him’, like the stench of the drains beneath the Statistical Section.

Christian Vigouroux, whose book on Picquart Harris cites as one of his sources, describes his subject as ‘a man without qualities’. Harris’s Picquart is no less enigmatic for being mildly sanitised. We have his anti-Semitic remark during Dreyfus’s degradation, Lazare’s charge that he was an anti-Semite, and his curt rejoinder when Dreyfus thanks him for what he did to secure his release: ‘I only did my duty.’ But we are not told that Picquart took to reading Drumont’s virulently anti-Semitic La Libre Parole.  ‘If Drumont hadn’t got in first,’ wrote Clemençeau, ‘what a splendid anti-Semitic newspaper Picquart and I could have run.’ It is more palatable, of course, for the modern reader to be told that this heroic champion of justice had an innate dislike of Catholics rather than Jews.