The French have an expression - entre chiens et loups - between the dogs and the wolves. It is a fanciful way of describing the twilight, the mysterious and uncertain time between day and night.
In the beautiful summer pastures of the Maurienne region of the French Alps, something mysterious, and wicked, has been happening in the twilight hours.
The events are uncertain but one thing is clear. This is, literally, a story about dogs and wolves.
Since the start of the year, 17 sheepdogs have been poisoned in the mountains of the Maurienne range, which rise to more than 9,000ft, just inside the French frontier with Italy.
The dogs have often died in great agony.
They include several of the Patou or Pyrenean mountain breed - enormous, white, misleadingly cuddly-looking dogs, which are trained to give their lives, if necessary, to defend sheep from wolves.
No one in the Maurienne range is quite sure what is going on - or, at least, few people admit to knowing much.
Everyone is clear about one thing, however. The killings are related, in some way, to the long battle that has been waged between shepherds and wolves - and between sheep-lovers and wolf-lovers - since the European grey wolf, Canis lupus, decided to recolonise France from Italy 16 years ago.
The most recent attack, earlier this week, destroyed - in the space of a few minutes - a four-month-old Patou puppy called Dom Dom.
Three other dogs, including Dom Dom's mother, Belle, were poisoned by balls of pork meat soaked in a chemical used in slug-repellent. They are recovering, after emergency intervention by the local vet, but may never be strong enough to work again.
"This can only have been the work of someone local, someone who knew the area," said Dom Dom's owner, Rene Grange, a shepherd in the hamlet of Les Villards, near Valloire.
"It is two hours' hard walking, and 1,000 metres steeply up hill from the nearest road to the Pain du Sucre [sugar loaf], the pasture where the sheep are grazing this week. You would have to know exactly where the night enclosures for the animals are. You would have to know how to avoid the hut where my two young shepherds were sleeping.
"The pork meat balls were left, some time during the night, most likely just before dawn, in a place where the dogs would be sure to find them. This is the work of a maniac - a madman. What if the meat had been found by a small child? There are tourists everywhere at this time of year.
"I bred Dom Dom myself and he was a wonderful young dog. It is sickening that he should die in such a way. But you can always replace a dog. You can't replace a child."
There have been a dozen similar incidents in the past eight months, which have killed 16 other dogs, including Dom Dom's father, Volcan, who died in early June.
Philippe Martin is the local vet whose prompt action in finding an antidote saved M. Grange's other dogs this week.
He said that the chemical placed in the meat balls is often found in slug poisons. It causes instant and catastrophic diarrhoea and lung failure in small mammals like dogs.
"They finish up dying completely dehydrated but, before that, they drown in their own bronchial fluids," he said.
Why should anyone want to destroy such beautiful sheepdogs? In such a brutal way?
Several theories have been put forward. The most obvious possible explanation is that the dogs are being poisoned by accident by wolf-haters.
There have been dozens of incidents of wolves being shot, or poisoned, illegally by shepherds in the French Alps in the past decade. M. Grange - and the Gendarmerie - have dismissed this possibility.
"Anyone who knew anything about the mountains would not try to attack wolves by leaving poisoned pork near sheepdogs," M. Grange, 45, said.
"This was a deliberate attempt to kill my dogs."
The second possibility is that this is some kind of revenge attack by militant pro-wolf activists, angry at the regular shooting and poisoning of wolves by French shepherds.
Some local people are convinced that this may be the explanation but it also fails to add up.
The shepherds in the Maurienne area, including M. Grange, are among those who have most successfully adapted to living with wolves since the animals began to infiltrate across the French-Italian border in the early 1990s.
There are now thought to be about 100 wolves living in France. A few have already left the Alps and crossed motorways and railway lines to recolonise the Massif Central to the west, and the Jura and Vosges to the north.
Most Maurienne shepherds have accepted the sheep-protection methods put forward by the French government's Plan Loup (wolf plan) published four years ago.
These include the permanent deployment of Patou and Beauceron dogs and young shepherds to watch the flocks day and night in the high summer pastures and the building of electrified enclosures to protect the sheep after dark.
There has been no wolf attack on sheep in the Maurienne massif for more than two years.
There has been no recorded wolf-killing in the Maurienne area in the same period.
Why would pro-wolf activists want to attack such a successful example of precisely the kind of man-sheep-wolf co-habitation that they have always insisted was possible?
The sheep-dog killings remain a complete mystery, then?
Possibly not. Daniel Vejux is a wolf expert and a member of the national committee of the main French wildlife study and lobby group, L'Association pour la Protection des Animaux Sauvages.
He is convinced that he knows exactly what is going on.
"There are some shepherds, like those in the Maurienne, who have now accepted that the wolf is here in France to stay. But there are others who have sworn never to accept wolves," M. Vejux said.
"There is a kind of civil war between shepherds, between those who accept government advice, and have taken measures to protect their sheep, and those who only care about one thing, driving the wolves out.
"These attacks on sheepdogs are meant to destabilise the systems which have been adopted to protect sheep from wolves. They are poisoning sheepdogs to intimidate the shepherds who are playing by the new rules."
M. Grange, the victim of the latest attack, refused to accept this explanation but looked uncomfortable when it was put to him.
"I don't know. No one knows. I can't say more than that. This is the work of a maniac. That's all I can say."
Other local people were equally defensive. The renting of summer pastures (alpages) to graze sheep brought from the coastal plains of the south of France - a system called transhumance - is an important local industry.
Many local people are involved, whether they are full-time farmers or not.
Transhumance used to be relatively easy work. The sheep were let loose on the alpages, the meadows just above the tree line, each spring. They were brought down in the autumn. In between, they were visited by shepherds occasionally. Otherwise, the sheep looked after themselves.
The return of the wolf, driven out of the French Alps in the 1890s, has changed all that.
"There are many local jealousies and grudges," said a shop-owner, who is himself involved in the sheep grazing industry but preferred not to be quoted by name.
"Some people have adapted to the new situation, the need to protect sheep from wolves, better than others. Some are very angry and don't think the wolves have a right to be back here, gobbling up their sheep.
"They think that they, the local people, are the victims. They blame ecologists and city-dwellers and think that they want to get rid of shepherds and sheep and fill the mountains with wild animals. Some of them are very angry. But there is a long way between being angry and going out to poison sheepdogs. A long way."
A local gendarmerie spokesman declined to comment on the suggestion that the dog poisonings were part of a pastoral civil-war.
"All possible leads will be followed up," he said.
"That's all we can say at present."
The sheep-grazing industry is an important complement to the income brought to the mountains around Valloire, high above the Maurienne valley, by skiing in the winter and walking and climbing in the summer.
Valloire is only 50 miles from Turin as the eagle flies but it is a picture postcard French mountain town n the kind that you see briefly on the television as the Tour de France sweeps by.
The 2008 Tour will, in fact, sweep briefly through the town of Valloire next Wednesday.
Normally, the coming of the Tour would be the dominant topic of conversation.
Not this year. The dog killings, M. Grange said, have created a "mood of fear and incomprehension".
"My two young shepherds, who are aged 21 and 23, thought they were taking on a peaceful summer job in the midst of the mountains. Now someone has crept past their hut at night and poisoned the dogs of which they had become very fond. They are confused and scared."