After three bomb attacks in two weeks, it is reasonable to assume that somebody has got it in for Aïssa Dermouche.
Is the grudge political or racial? Or is it merely personal? French police are mystified. The French nation is perplexed.
The series of explosions in the quiet city of Nantes has caused no casualties and no serious damage - except collateral damage to the reputation of a man who was supposed to become a powerful symbol of racial and religious integration.
Last month, Mr Dermouche, born 57 years ago into a poor farming family in Algeria, became the first immigrant to rise to the rank of prefect - the élite corps of uniformed officials which administers the French state.
His qualifications were undisputed. The government's timing was transparent. While the country was wracked by an anguished, and occasionally farcical, debate about the banning of the Muslim headscarf in state schools, Mr Dermouche's appointment would be the living proof that immigrants could succeed and that France was not anti-Islam.
Four days after his appointment as the prefect of the Jura département on the Swiss border, a bomb exploded in the engine of his car, parked near his home in Nantes. The car, a Saab, was wrecked.
French politicians issued thundering condemnations of what they assumed was a political act, carried out by a splinter group of the far right, an extremist Islamist movement or, possibly, by Breton separatists. (Nantes, at the mouth of the Loire, is historically Breton but was severed from Brittany in the division of France into administrative regions in the 1980s.)
Three days later, police arrested three men. One was a physiotherapist, aged 60, who had once lived with Mr Dermouche's divorced second wife and had quarrelled in public with Mr Dermouche. The others were men in their 20s who were linked to Mr Dermouche's estranged daughter, aged 18. After two days of questioning, the men were released.
Last Sunday - a week after the original explosion - a small bomb wrecked the entrance to the Audencia business school in Nantes, where Mr Dermouche has been the much-praised principal since 1989.
Soon afterwards, police revealed that the original car explosion, far from an amateur affair, had probably been carried out with TATP (triacetone triperoxide), the chemical used by the so-called "shoe-bomber", Richard Reid. TATP is not hard to come by, but is not easily manipulated by amateurs.
Finally, three days ago, a small bomb scorched the entrance to a lycée in Nantes attended by Mr Dermouche's son, 15. The third explosion was even weaker than the others - "little more than a bombette, hardly bigger than a firework", according to the head of the school.
Mystery and confusion reign. Police are treating the three bombs as part of a series. The materials used in the college and school explosions have not yet been established. The three men arrested and then released appear to be in the clear. Investigators are turning once again towards possible political or racial motives.
Half a dozen claims of responsibility for the bombings have been made, purporting to come from white supremacist and Islamist groups. None is taken seriously by investigators. France's anti-terrorist squad has not been consulted. The investigation under way is, nominally, for "wilful damage to property"; in other words, for severe vandalism, rather than terrorism.
In the meantime, Mr Dermouche's reputation as a revered college head and shining example of personal probity, upward mobility and racial integration has been dented - although certainly not destroyed.
The French privacy laws prevent detailed exposure, but the French press has spoken of his "complex private life", his two divorced wives and his troubled relationship with his daughter and his second ex-wife. (He has since married for a third time.)
Speculation has also arisen about possible professional jealousies, because of his reputation as an authoritarian principal of the Audencia school and the disclosure several years ago that he had mildly inflated his own academic qualifications. Mr Dermouche's friend, the philosopher Alain Etchegoyen, complained in an article in the newspaper Le Figaro last week that the newly appointed prefect was an intensely private man who had been put through a horrible experience. Ever since the Nantes police had revealed that they were questioning people connected with his family, Mr Dermouche had seen "his whole personal story spread out in the press".
Whatever the motive for the bombings turns out to be, the saga is a gift to the racist far right in France. Mr Dermouche's elevation to prefect was meant to show that Muslims and immigrants can succeed in French society. It will be used - is already being used - by Jean-Marie Le Pen's National Front as proof of the opposite: that wherever Muslims go, troubles follow.Reuse content