It was almost too easy. Hidden away in a residential area at the edge of the Bois de Boulogne, the 15-room Mus'ee Marmottan houses one of the world's great Impressionist collections in the intimate and peaceful atmosphere of a private home, a combination perfect for art-gazing -- and art theft.
Just after opening its doors a week ago Sunday, a group of men suddenly produced revolvers. In five short minutes of work they carried off nine priceless paintings, including Claude Monet's ``Impression, Sunrise,'' which gave Impressionism its name.
But why? Museum officials, art dealers, and police investigators remain baffled.
The paintings are too well known to find a buyer. In addition to the celebrated Monet, the thieves took four other Monets, two works by Pierre Auguste Renoir, a Berthe Morisot, and a Narus'e.
Although initial estimates put their worth at around $12 million, a spokesman here for Christie's auction house said that ``no value can be put on such objects of a national patrimony.''
For this reason, wild speculation surrounds the motives. Some suggest left-wing terrorism. Others speculate straight ransom. And others even suspect a type of sinister Dr. No-style private collector who will hide the works in his vault.
The choice of paintings stolen also remains enigmatic. To be sure, the nine taken were all important paintings. But why take a lesser-known Narus'e when the museum boasted many masterpieces, including many Monet waterlilies?
``The hard truth is that we just don't know yet,'' police commissioner Jean Simolet, heading the investigation, conceded to the Monitor.
Only one thing is clear: The burglary represents a new turn in art theft. While there have been six major museum robberies in France during the past decade, none took place in broad daylight.
``This was a holdup,'' explained Jean-Claude Vincent, head of the special French police unit charged with recovering stolen art objects. ``Generally, art thefts are carried out at night by breaking and entering.''
And yet the Marmottan burglary was professional.
Marianne Delafont, in charge of the museum's exhibitions, told the Monitor that the thieves seemed to know that the museum's alarm system was turned off during the day. She added that they also seemed to know that the museum's seven guards carry no arms, and that no permanent security device exists to set off an alarm even if an innocent visitor tampers with a painting.
``They came in right after the museum opened in the morning,'' she said. ``They locked the janitors in a cupboard, stood guard over the visitors, and took what they wanted. They were cool.''
Conceivably, police said terrorists could use the paintings as bargaining chips, just as they use hostages. Once before, in 1978, an extreme-left group, Direct Action, claimed responsibility for the burglary of a museum in the Paris suburb of St. Germain-en-Laye. But so far, no communication from it or any other group has been received.
A straight ransom also seemed a possibility. In the past, there have been some quiet negotiations with go-betweens about stolen art, mostly conducted by insurance companies. According to dealers here, these almost always concerned private works of art.
Amazingly, none of the art in France's state museums is insured.
``Were we to insure all the masterpieces in all our museums,'' explained Culture Minister Jack Lang after the theft, ``there wouldn't be any funds left for anything else in the Culture Ministry.''
At the Marmottan, which is run by the public Acad'emie des Beaux Arts, Ms. Delafont said that insuring the collection would cost almost a million dollars a year, a fee the museum can't possibly afford. ``We only insure the paintings when we lend them out for an exhibition,'' she explained.
Perhaps the thieves still mean to threaten the French government to pay up or see the masterpieces destroyed. But Mr. Lang insisted, ``We won't be blackmailed or extorted.''
Police think a tough stand provides the best hope of eventually getting the paintings back. In many past art thefts, the thieves have finally tired of running and abandoned their booty. This happened, for example, after the last major art theft here, in 1976, when 118 paintings by Pablo Picasso were stolen from the Palais des Papes in Avignon.
So the best hope is to wait. In the meantime, Delafont says, the Marmottan plans to take stricter security measures, including keeping the alarm on during opening hours. The museum reopened last Thursday.
``We have more visitors than normal,'' she reported. ``Lots of people are coming to see where it happened.''