Were it not for a knock on the door in 1945 Amsterdam, Han van Meegeren might have been forgotten. He was a small and dapper man, a Dutch artist of limited ability. He was also a forger — and the force behind what a new book says was the greatest art hoax of the 20th century.

Van Meegeren passed his paintings off as newly discovered works by renowned 17th century artist Jan Vermeer. He fooled experts and collectors, including the second-most powerful man in Nazi Germany, Hermann Goering, and pocketed the equivalent of $30 million before he was unmasked.

Edward Dolnick, author of The Forger's Spell, says there were several reasons why van Meegeren, who tried his hand at imitating Franz Hals and other Dutch painters, decided to make a career of Vermeer.

"One was that he was just about the greatest brand name of them all," Dolnick tells guest host Linda Wertheimer. "In art, this is the equivalent of Rolls-Royce or Tiffany or something — if you can get away with Vermeer, that shows how terrific you are and it's where the money is.

In addition, Dolnick notes, Vermeer's biography is almost a complete blank. The absence of information left "lots of elbow room to fill in the gaps as you saw fit because nobody knew what the real story was," he says.

That Vermeer produced only about 35 or 36 paintings was also helpful. Other major painters of the time, such as Rembrandt, typically created 10 times as many works. "So for art historians," Dolnick says, "one of the great questions is: Where are all the others? So you might guess that there once were more and they were lost, which is what a forger would like you to guess. It might also be that he simply painted terribly slowly. No one knows."

When van Meegeren settled on Vermeer, he did extensive research and experimentation with canvasses, paints and aging techniques. And he developed an ingenious way to hoodwink the experts through the use of plastics.

The forger's biggest challenge was making a painting that was only a few months old seem as if it were 300 years old. It takes decades for an oil painting to fully harden — if you press your finger into a blob of paint on a recent painting, you could probably make a dent. Van Meegeren needed to make paint that would look old, which meant it had to be dry.

So he bought a pizza oven, Dolnick says, and tried time and again to mix a paint that could withstand the heat of the oven and harden, but not lose its brilliance. Time and again, his experimental paints burned up or melted. Then he hit on dissolving a small amount of plastic into the paint and that let him get away with his colossal hoax.

Although van Meegeren made a number of painting that mimicked Vermeer's style — tiny pictures with rich fabrics, clear blues and bright yellows, light streaming in from the left — they were unsuccessful. Instead, he decided he had to create works that were vastly different because of a phenomenon that Dolnick refers to in his book as "the uncanny valley."

"What he learned was that if you come close to getting an imitation just right, the closer you come for a while the more convincing people find it," Dolnick says. "But when you get ... almost all the way there but not quite, at that point — and no one quite knows why — people begin to look closer and suddenly they focus not on how close this imitation is to the real thing, but on the last little gap that keeps it from being real.

"Van Meegeren found that a forgery that was close was almost worse than if he hadn't tried at all, because as soon as it was close, the experts would focus on the difference between the forgery and the real thing," he says. "What turned out to be a much better strategy for van Meegeren was to make a painting that had a few hints of Vermeer but that wasn't like any of the known Vermeers, and then let the experts fill in the gaps themselves. Let them say, 'Aha, didn't I always tell you that Vermeer had much more to him than you thought? It's not all ladies reading letters, it's sometimes completely different paintings like this new one we've just found.'"

Taking a huge gamble, van Meegeren began to make paintings that people might think looked strange but would say was a Vermeer.

It paid off handsomely.

"The experts didn't say, 'This painting purports to be a Vermeer but doesn't look like any of his. I wonder if maybe it's not,'" Dolnick says. "What they said is, 'It doesn't look like any Vermeer, therefore Vermeer was even a greater genius than we knew. Who knew he was such a multifaceted man?'"

The painting that made van Meegeren was called "Christ at Emmaus," after the Bible story in which Christ reveals himself to several disciples after he has risen from the dead. It was different from any Vermeer in that it was religious in subject matter and much larger than anything Vermeer was known to have done. In essence, the painting was "proof" for the experts of what they had thought must exist but had never seen.

"Christ at Emmaus" was so well received that van Meegeren began churning out one biblical painting after the other, each selling for millions of dollars. "Now they didn't have to look like the Vermeers that we know, they only had to look like the Vermeer that he had introduced into the accepted works," Dolnick says. "So van Meegeren's task got easier and easier."

One of the most famous of the series was titled "Christ with the Woman Taken in Adultery," which Dolnick says was a major triumph because of whom he fooled into buying it.

"At this point, essentially no Vermeers had turned up in centuries. All of a sudden, they're turning up practically every six months and the collectors want in on this game," Dolnick says. "One of the biggest and greediest collectors of the day was Hermann Goering, the No. 2 man in Nazi Germany. ... He takes looted paintings and trades 137 of them for this one Vermeer, which is going to become one of the jewels of his collection."

But that painting was also van Meegeren's undoing.

The Nazis were known for meticulous record-keeping, and after World War II ended, the paperwork for Goering's prize "Vermeer" listed van Meegeren's name. When the police rapped on van Meegeren's door in 1945 to question him about what they thought was a routine matter, the forger didn't have a very convincing answer.

"Most forgers fool one person too few, that's what does them in. Someone says, 'Wait a minute, this is wrong,'" Dolnick says. "That never happened with van Meegeren. What happened with him was this mix-up with Goering, which brought the authorities on the run."

Van Meegeren was tried, convicted and sentenced to a year in prison in 1947. Nearly two months later, he died of a heart attack without serving even a day.

Ironically, he died a hero.

Although van Meegeren had hobnobbed with the Nazis during the occupation of Holland, he styled himself as a Dutch patriot during his trial.

As Dolnick puts it: "He says, 'Of course I sold it to Goering, I knew what better person to con than this great Nazi bag of wind. How could a person demonstrate his patriotism, his love of Holland more than I did by conning the great enemy of the Dutch people?' And the Dutch ate it up. They liked him."

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