The Purloined Painting.(Charles Hill investigates art thefts)

It's every millionaire's worst nightmare: waking up to find a home stripped of priceless artwork overnight. If that fails to arouse your sympathy, consider that it happens regularly in museums, too; treasures worth billions of dollars are swiped every year in audacious heists from public galleries around the world.

Thanks to Charles Hill, there's hope of getting them back. The former head of Scotland Yard's art-and-antiques squad is one of a handful of specialists feared in the insular criminal underworld of stolen art. Bookish and genial, Hill (who won't permit his picture to be published so he can remain anonymous to the thieves) made a name for himself when he recovered Edvard Munch's well-known painting "The Scream" after it was stolen from the National Gallery in Oslo nearly a decade ago. Since then he has returned works by Vermeer, Goya and Turner to their rightful owners. So when a $50 million 16th-century sculpted saltcellar went missing from Vienna's art-history museum last month, officials knew right away whom to call.

Hill has his work cut out for him. Most stolen art is never recovered, not least because it's a low priority for overstretched police forces around the world. In Britain, Scotland Yard's art-and-antiques division has a skeletal staff. "The problem is that art crime is international, and there's no international body you can turn to," says Hill. "Interpol is a message-switching system. You pass a message on to Interpol, and they pass the message on to someone else. When people say, 'Interpol's on the job,' that means absolutely nothing. Which leaves a big gap in the market for me." What's more, art thieves are generally savvier and better educated than other kinds of criminals, and their transgressions confer high status among the lawless. "It's considered a high-class crime in the criminal's mind," says Hill. "It's a sort of fashionable accouterment for a criminal who starts doing hubcaps when he's young and then moves up the chain."

Often paintings end up being used as collateral for loans or in drug deals. Thefts tend to be committed not by individuals but by groups. And after nearly three decades in the business, Hill has crossed paths with most of the groups involved. In many cases he knows as soon as he sees the crime scene exactly who's involved. "I don't look at the forensic side; the police will do that," he says. "I ...