Seven weeks after the brutal murder of four people on a mountain road in the French Alps, the dark mystery of Annecy remains intact. But media speculation thrives.
More pieces are gradually being added to the jigsaw by a joint Franco-British investigation but, whichever way the puzzle is put together, there are important pieces which do not fit.
In the meantime, public understanding in both countries has been muddled by far-fetched theories and incorrect reporting. The explanation is partly to be found in the secrecy rules of the French criminal justice system.
In France, once an investigation is handed to an examining magistrate, it is covered by "le secret d'instruction" (the secrecy of the inquiry). Even basic facts are not to be divulged to the public.
Since the media, understandably, detests a news vacuum, there are inevitably leaks. Some are genuine; others less so. Some of the leaks to the French media are reported responsibly in the British press. Some are "spun" out of recognition. Result: confusion in both countries and criticism in Britain of the "incompetence" of the French investigation.
The public prosecutor for the Annecy area, Eric Maillaud, says that he is aware of the problem but that his hands are tied.
"If there is a piece of information published which is manifestly false, then I have tried to make that clear," he told the Independent. "But I cannot get into the business of confirming or denying every story without breaching our rules or without revealing information that we would rather keep to ourselves."
It is more than a month since Maillaud, the investigation's official spokesman, gave a press conference. Would it not be a good idea if he was to give an official update to clear away the myths?
"I will consider it," he said. "But at present I have nothing very new to tell you. If we do have another press conference, it will be jointly with the British investigators."
Meanwhile, the "known knowns" of the Annecy mystery - those things which have been officially confirmed and those things which have been reliably reported and not officially denied - offer some insight into the last hours of the four victims.
Soon after 4pm local time on Wednesday September 5, a British cyclist found a scene of unbelievable butchery on a remote layby on a forest road above the village of Chevaline.
Saad al-Hilli, 50, an Iraqi-born engineer, his wife, Iqbal, 47, and her mother Suhaila al-Allaf, 74, who had been caravanning nearby, had been shot repeatedly in their wine-coloured BMW estate car.
A local man, Sylvan Mollier, 45, lay dead beside the car. His body had been dragged from where he was originally attacked.
Seven-year-old Zainab al-Hilli was found alive outside the car, beaten savagely about the head and face, and wounded by a gunshot in her shoulder. Her sister, Zeena, aged 4, was found eight hours later, unharmed but terrified, hiding under her dead mother's legs.
A British cyclist, Brett Martin, a retired RAF pilot, had been overtaken by the local cyclist, Mollier, on the steep, winding climb to the layby a few minutes earlier. When Martin arrived, the engine of the BMW was still running.
A preliminary ballistic and forensic report, leaked last week, found that only one gun was used, a 7.65mm automatic. French media say that this was a Luger P08 - an old-fashioned gun not used by professional killers.
Martin saw a green truck and motorcycle descending the bumpy road from the murder scene. The truck is believed to have belonged to the forestry commission. There are eyewitness reports that a motorcyclist was behaving oddly on a remote road nearby that afternoon.
Much of the Franco-British investigation has focused on the possibility that al-Hilli was targeted because of a family quarrel over money, or because of his work in the aerial surveillance industry, or for some reason connected with his Iraqi past.
Although all possible explanations remain open, there have been hints in the French media - not confirmed by Maillaud - that the investigation is shifting towards the possibility that the murderer was a "lone wolf" or psychopath.
But why there? Why them? Why with such an old-fashioned gun? And why was little Zainab al-Hilli left alive?
The "real" target was the French cyclist, Sylvain Mollier, not the three members of a British-Iraqi family. The "proof" is that, of the four, Mollier was "shot first".
Inconvenient fact: it is scientifically impossible to prove who was shot first.
A large amount of money found in an Al-Hilli family bank account in Geneva (only 50 minutes' drive from the murder scene) holds the key to the killings.
Inconvenient fact: The Geneva account contains much less than the 1 million ($1.6 million) or so reported.
The Israeli secret service may have commissioned the murders. Mollier was a "nuclear scientist"; too sinister to be a coincidence. Was he engaged in furtive, pro-Iranian dealings with Saad al-Hilli, an Iraqi-born engineer?
Inconvenient fact: Mollier was not a scientist but a middle-ranking employee of a local factory supplying specialist metals to the nuclear industry. If al-Hilli was engaged in some kind of nuclear-smuggling tryst in the mountains, why did he bring his family?