The officer is Georges Picquart, a major in the French army in 1895 when the story begins. The spy could be one of two people - either Captain Alfred Dreyfus, a French-Jewish army officer wrongfully convicted of passing secrets to Germany, or alternatively the real spy, another French army major.
At a time when anti-semitism was rife and not particularly frowned upon, and when diplomatic relations between France and Germany were very low due to the latter's annexation of the Alsace-Lorraine regions, the wishy washy evidence against Alfred Dreyfus was enough to have him convicted of treason in spying for Germany. Public humiliation and exile followed. Georges, who was involved in the arrest and the trial of Dreyfus, was promoted to the rank of colonel and became chief of an intelligence unit within the French military. This appointment gave him access to all the material and evidence against Dreyfus, the result being he uncovered a conspiracy that covered the tracks of the real spy and made Dreyfus the scapegoat. The first half of the novel is Georges discovering these facts, the second half is what he tries to do about this massive miscarriage of justice and bring the true spy out into the open. Very, very John Le Carre.
The case was an absolute sensation in its day. The overwelming negative public opinion towards Dreyfus, mainly on account of his being Jewish, made it very difficult for Dreyfus' supporters of which there were quite a few, to highlight the injustice that had been done. Within the military Georges's whistleblowing nearly cost him his life, but eventually in 1899 Dreyfus was freed, and in 1906 officially exonerated.
Robert Harris, a prolific writer, has made good use of his early journalistic career in now writing excellent historical fiction. He has the ability to make history come alive, weaving actual events and settings around the lives of real and made up characters. Even though this book is classified as a novel, all the characters were real people, and everything that happens in the book is also true, the author drawing on personal letters, police reports, newspaper articles, official documents, court transcripts. Despite all the factual material, he has still managed to instill character, personality and thought processes into his main characters, so it does not feel that one is reading a historical account, but rather a great story. I wouldn't say it is a page turner, full of excitement, intrigue and action; rather it is quietly gripping, sinister, and highlights quite scarily, how dangerous it is for one man who, singlehandedly, decides to take on the might of the French military playing them at their own game.