After The Scream was stolen from the Munch Museum, this reproduction appeared at the Guggenheim—as part of a 2006 campaign launching dark chocolate M&M’s. A reward of 2 million M&M’s was offered for the picture’s recovery.

After three armed men in ski masks stole four paintings by Cézanne, Degas, van Gogh, and Monet worth about $163 million from a Zurich museum last February, the police said that one of the men spoke German with a heavy Slavic accent. It was possible, the police said, that the paintings were sticking out of the thieves’ car as they made their getaway. Four days earlier, thieves stole two Picassos worth about $4.4 million in a nearby town.

Who is the thief with the heavy Slavic accent? Is he the man who returned two of the paintings—Monet’s Poppies near Vétheuil (1879) and van Gogh’s Blossoming Chestnut Branches (1890)—eight days later, when the works were found on the backseat of a white car parked outside a psychiatric hospital several hundred yards from the museum?

As ARTnews went to press, neither the thieves nor the other paintings had been found. The works still missing are Degas’s Count Lepic and his Daughters (ca. 1871) and Cézanne’s Boy in the Red Vest (ca. 1895).

The Art Loss Register, which has the world’s largest database of missing or stolen art, states that there are 79 works by Degas and 52 by Cézanne missing or stolen. Picasso heads the list with 574.

The four paintings were stolen from the Foundation E. G. Bührle Collection, which also has works by Renoir, Gauguin, Manet, Picasso, Braque, and medieval wood carvings. Bührle, who died in 1956, was one of Switzerland’s most important art collectors. During World War II he was a major arms supplier to the Nazis and later was the largest Swiss buyer of art confiscated from Jews by the Third Reich. The museum is housed in a villa near Bührle’s former home.

To find out more about the recent thefts, I called four of the world’s leading art sleuths.

“The thug who spoke German is part of the Balkan Bandits,” said Charles Hill, formerly a top member of Scotland Yard’s fabled art and antiques squad, and now a private investigator in London. Among his exploits: he helped arrest a thief who kept cash stuffed in a Kellogg’s Corn Flakes box on his desk and another who said he was “Peter Brewgal” (it rhymed with “bugle”) and who really had stolen a Pieter Bruegel.

How does Hill know about the thug? “If you speak German with a heavy Slavic accent, there’s a good chance you’re from the Balkans.”

I asked Dick Ellis, who was in charge of the Scotland Yard squad from 1989 to 1999 and is also a private investigator in London (he helped recover, among many other works, Buddhas looted from the Pakistan–Afghanistan region): What does it mean that one spoke with a heavy Slavic accent?

“It means one of them was Slavic,” he said, adding: “Balkan Bandits? It’s a possibility. Organized-crime syndicates recruit all sorts of people. The fact that you have one Slavic in the group doesn’t mean they’re all Slavic.”

What does Tom McShane, a former agent of the Federal Bureau of Investigation who says he recovered millions of dollars worth of stolen art in odd places—a van Gogh in a gas station, a Rembrandt in the bathroom of a tiny antiques shop, and a Rubens in the backseat of an old van—think of the theft?

“When a bunch of criminals get together,” he said, “we can call them Balkan Bandits or Bayonne Bandits or whatever. They’re just a bunch of thieves out to make a score. It goes from A to Z. It’s possible there wasn’t enough security. [The Zurich police said an alarm went off.] It’s terrible. A lot of museums are like that. It entices these thieves when they see vulnerability. It’s like leaving your Rolls-Royce in the street with your keys in it.”

The fourth sleuth I called was Robert Wittman, senior investigator of the FBI’s Art Crime Team, who has been involved in the recovery of more than $150 million worth of stolen art and artifacts.

He had nothing to say about Balkan or Bayonne bandits. “It’s terrible that someone would need to steal these works,” he said. “If we pick up any leads, we’ll be happy to work with our colleagues in Switzerland.”

So who are the Balkan Bandits?

“They’re the greatest predators in Western Europe for high-profile art robberies and burglaries,” Hill told me. “They’re various groups of Serbs, Croats, Kosovar Albanians, Macedonians, and Montenegrins. Maybe they were inspired by the thieves who stole the two Picassos.

“There’s been a significant change in the last decade among art thieves that’s very worrying. They charge in fully tooled up. They are now armed. These are violent thieves. Even the Mafia didn’t steal at gunpoint prior to this group. I’ve found that violent thieves generally don’t know what to do after they have stolen the paintings. These guys sometimes panic. Sooner or later it dawns on them that stealing was the easy part. Now comes the hard part. What do you do with it? You can’t hang it on a wall; you can’t sell it on the open market. The paintings are priceless and worthless at the same time. They have limited use in the criminal world as collateral.

“Sometimes stolen art is used to launder drug debts. Say you owe some guy 20 grand for selling you drugs. You steal a painting worth a million or so, and you hand it over, and you say, ‘I’ll pay you, but have this in the meantime.’”

Sometimes, too, information about stolen paintings can be helpful to a criminal.

Hill continued: “Remember the theft of one version of Munch’s The Scream that was stolen from the Munch Museum in Oslo along with Munch’s Madonna in 2004?

“The police solved it through a man who had been convicted of armed robbery. He bartered his way to a better life in prison. I heard that after he was convicted and sentenced to 20 years, his lawyer said to the cops that in return for conjugal rights with his girlfriend and a published reward of 2 million M&M’s candies, he’d arrange to have the pictures returned. He reckoned he could go through the 2 million in 20 years. The paintings were later recovered.”

Back in 2006, M&M’s candy, after launching a new ad campaign at the Guggenheim Museum for what it called its “newest masterpiece”—dark chocolate M&M’s—announced that it was offering a reward of 2 million dark chocolate M&M’s for the return of The Scream.

Did 2 million M&M’s ever get to Norway?

“Norwegian authorities are continuing to review the case around the recovered paintings,” a spokesman for M&M’s e-mailed me. “For that reason, we have been asked by them to postpone final disbursement of the reward until we get their approval. Until then, I’m afraid we are unable to announce any details.”

Will the M&M’s go to the thief? “Our intention is to return it to the police,” the spokesman said. “We’d never give a reward to a convicted criminal.”

I called Iver Stensrud, who is Oslo’s assistant chief of police.

“We’re waiting for the final court case, possibly by this summer,” he said.

Who will get the 2 million M&M’s?

“We have proposed that instead of the candy, a check for 140,000 Norwegian kroner [about $26,000] be sent here. That’s what the candy is worth. We are not allowed to take the money. We have a plan. The money will go to the Munch Museum.”

Could he comment on the thief who supposedly bartered his way to a better life in prison? “We have no comment on that.”

The M&M’s spokesman confirmed Stensrud’s account. How come no M&M’s will go to Norway? “There was a question of the logistics of sending it,” he said. “Moreover, sending the cash is much more useful since it will go to the museum.”

Could he elaborate on the logistics? “Two million M&M’s equates to 40,000 bags of M&M’s—about 2.2 tons.”

Milton Esterow is editor and publisher of ARTnews. Amanda Lynn Granek is assistant to the editor and publisher.