A few weeks later another work he had bought from Clive Belman, Ben Nicholson’s colorful Mexican, went up for auction at Sotheby’s in New York. Again the outcome was a disappointment: The painting sold for £5,000 less than Nahum had paid for it.

Two in a row, he thought. Was it a coincidence that both works had come from the same source? Nahum took another look at the Crucifixion panel. The signature had seemed genuine enough, but on closer inspection it looked slightly off-kilter and divorced from the composition. And when he thought twice about Mexican, it suddenly seemed too bright by a half.

In early 1995, Nahum got a call from a man named Hans Meyer, a Sussex horse breeder and art collector who was organizing a memorial concert for the victims of Auschwitz. The concert was to be financed through the sale of donated paintings and manuscripts. The organizers were planning a gala performance by the Auschwitz Memorial Orchestra in August, seven months hence, featuring the conductor Michael Tilson Thomas and several well-known singers. Would Nahum be interested in buying some of the donated works?

Nahum asked Meyer to send a list, and a few weeks later he received a long letter from Meyer describing works by the German artists Willi Baumeister and Max Liebermann and the Romanian painter Arthur Segal. All were in excellent condition and had good provenance, Meyer said. In addition, there were three British paintings for sale: a Ben Nicholson entitled Barndance, and two works by the urban landscape painter L. S. Lowry, a secretive man who had a reputation as an eccentric prankster. During his lifetime he had produced thousands of paintings and drawings, many of which depicted “matchstick men” in drab industrial surroundings. He often drew sketches on napkins and the backs of envelopes and gave them away. Dozens of these obscure Lowry pieces scattered around Britain were now worth thousands of pounds.

Meyer’s letter also contained an update on preparations for the Auschwitz concert. Vanessa Redgrave had agreed to perform a spoken prologue entitled “Inherit the Truth,” he said, and the conductor and brass virtuoso David Honeyball had been named musical director.

Nahum asked Meyer for photographs of the Lowry works. When they arrived and he opened the envelope, it was immediately clear that they were wrong. The figures looked mechanical, as if they had been drafted with a ruler. Meyer said they had been restored recently; they were perhaps not the best examples of Lowry’s work, but they were genuine.

When Nahum saw a photograph of Nicholson’s Barndance, he was even more suspicious. The painting was off by a mile. Was the Auschwitz concert a front for passing off fakes? If so, did Meyer know it, or was he being scammed himself?

Several days later Nahum received another letter from Meyer, this one notable for its scatterbrained urgency. “You probably know that February 1995 is the 50th anniversary of the liberation of Auschwitz by the Soviet Army,” Meyer wrote. “Our committee has now made the major decision regarding the program of the concert, which consists of fewer choral works, which have been replaced by excerpts from symphonies. Later in January we have to pay a further installment to the musical director, and our immediate requirement (rather desperately) is to raise the money to do this.”

The letter made reference to other works of art that would soon be available and asked whether Nahum was still interested in Barndance. “We have an urgent need to raise some money quickly. We would very much appreciate a quick settlement, or a deposit with the final payment at a time convenient to you. We have a guarantee of a substantial contribution ($50,000) being made at the end of January from a member in America, yet in the meantime we are scraping around for funds!”

Nahum called Meyer and asked him to send Barndance over. As soon as he unwrapped it, his suspicions were confirmed: It was a fake. On the reverse were two familiar labels, identical to those on the back of Mexican.

Nahum had spoken to other dealers and was aware of several bogus Nicholsons on the market that had come from the collection of a John Cockett. He suspected that Belman, Drewe, Meyer, and Cockett were connected. The provenances of the works were similar: They each included receipts and catalogs from the 1950s and stamps from the National Art Library or the Tate Gallery. One receipt in particular stood out. It detailed the purchase by the painter Norman Town of two works by Nicholson; one of them was Barndance, purportedly made in the 1950s. Nahum knew Norman Town and thought it unlikely that the impoverished artist had ever been able to afford a Nicholson.

Fakes were nothing new to Nahum. A quarter of the works he saw every year were fakes or had serious problems of authenticity. There were several distinct levels of forgery or misattribution: the outright fake; the genuine but unsigned work to which a dealer or a restorer added the artist’s signature in order to increase the price; and the piece that had been incorrectly ascribed to the artist, knowingly or not.

So many works of art flooded the auction houses that there was never enough time to catalog and check each one properly. Occasionally, the auction houses would turn a blind eye to a questionable item. In April 1989, a Russian offering in London featured two outright fakes and one dubious picture that had been badly restored and then signed by a forger. The auction house had been warned about these but had gone ahead with the sale.

In Nahum’s considered opinion, it was the dealer’s job, in this new world of mass-marketed art, to protect the public from fakes of every kind. Most of London’s reputable dealers were dependable: If one of them sold Nahum a fake, or vice versa, the money was refunded immediately, no matter how many years had passed since the sale. Nahum didn’t pull his punches when he came across a fake. Certain gallery owners might politely back out of a deal, claiming a lack of interest, but Nahum had no qualms about denouncing a work on the spot. He called Hans Meyer.

“Did John Drewe give you these paintings?” he asked point-blank.

Meyer confirmed that Drewe was the source.

Nahum said he thought the paintings were fake and ordered Meyer to take them off the market. Then he photocopied the provenance documents, photographed the front and rear of Barndance, gathered all the material he had on the Lowry works and the pieces from Clive Belman, and called a detective he knew on the Art and Antiques Squad. With the casual grace derived from his years at Sotheby’s, he said that he had come across evidence of a large-scale conspiracy to deceive the art market. He offered to share it with the Art Squad, and invited them to pop down to the gallery.

“I think you might want to see this,” he said.

“Unlike the Mafia, the art world glitters,” he liked to say.

Gimpel sent the painting to his longtime restorer, Jane Zagel, ostensibly to have a damaged section of the work repaired. What he was really after was her unbiased opinion. If she thought the work was off, he would definitely hear about it.

Zagel was one of London’s top restorers. A gregarious woman with short red hair and rosy cheeks, she had been in business for thirty years. She was familiar with most forgery methods and had worked briefly in the same restorer’s studio once used by Eric Hebborn, one of the twentieth century’s most infamous fakers. Whenever a new piece came in, she liked to have it around the house for a few days before she touched it. She would hang it up in her studio or in the bedroom and take in the draftsmanship and brushwork, as if trying to decipher a code.

Shortly after receiving the Nicholson from Gimpel, she awoke in the middle of the night with a feeling that something wasn’t quite right. She went up to the third-floor studio, switched on the light, and examined the watercolor, which was propped on an easel in the corner. The geometric shapes seemed flat and motionless, like toys in an empty playground. There was none of the lively interplay that characterized Nicholson’s abstracts. He had used layer upon layer of paint to bring his figures to life, but the shapes in Gimpel’s piece had a paint-by-numbers look.

Even the most mediocre artist has his own approach, a particular variation of pressure that thins the line while rounding a curve or thickens it when it runs free, but the underlying pencil marks in the Nicholson were mechanical and unwavering. They had been made with a 3B or 4B pencil, a dark grade of lead nearly as soft as charcoal that smudged easily and tended to dull over time, but they were shiny and distinct even though the piece was supposedly painted in 1938.

Of the thousand or so pieces Zagel worked on each year, only about five of them turned out to be fakes, a relatively small number compared to the percentage of fakes in the overall art market. She was almost certain that the Nicholson was a forgery, but to prove it she would have to pick the work apart in the least invasive manner possible.

She turned the watercolor over and put it back up on the easel. It was mounted on a piece of hardboard. She removed the tacks, which she suspected had been artificially rusted with saltwater, an old forger’s trick. Then she removed the hardboard and examined the paper on the back.

It was fairly common practice to use a false backing on a forgery. The forger would take a sheet of antique paper contemporaneous with the purported age of the work, then glue it on in order to disguise the modern paper or canvas. The paper on the Nicholson had an off-white tone that was appropriate to an older work, but it certainly didn’t date back to the late 1930s. Zagel could tell by the texture and weave that it had been produced after World War II. She dabbed at the edges with a wet Q-tip and watched as a transparent jellylike substance oozed out—the typical reaction of modern conservation glue when it was moistened. Carefully, she peeled the paper back, revealing another sheet of paper, this one thick and pure white, with a scrawled notation that read, “TOP—BEN NICHOLSON 1938.”

This sent her into a tizzy. Top? Wouldn’t Nicholson have known which side was up and which was down on his own painting? She filled an eyedropper with water and squeezed gently. A single drop landed on the paper and wobbled for a moment before it steadied itself into a perfect sphere. As paper ages, it becomes more and more absorbent. If this paper had been made in 1938, its weave would have broken down by now and the drop of water would have melted into it. The Nicholson’s paper was still water-resistant, as if it had just come from an art supply shop—which it probably had, Zagel thought.

She flipped the work over and studied the composition again. Although she strongly suspected that the piece was worthless, she used extreme care to remove a tiny sample of paint. The goal of every competent restorer is to disturb the original work as little as possible, even if it is a suspected forgery. A two-hundred-year-old watercolor that had been faded by sunlight, for example, should not be returned to the owner looking as if it had been painted yesterday.

Through a microscope Zagel could see that the paint on the Nicholson was a gouache, an opaque type of watercolor. It was a cheap version, heavy in chalk of the same grade and in the same proportion found in children’s poster paint. Gouache fades as it ages, many of its colors tending toward a light gray. Some gouaches are more fugitive—fade more quickly over time—than others, particularly the yellows, and ever since she had first seen the Nicholson Zagel had been suspicious of the brilliant sunburst at the edges of the composition. She zeroed in on a lemon-yellow orb.

Dabbing a #1 sable brush in distilled water—the brush was the smallest in her armory, just five hairs thick—she peered through a magnifying glass, leaned over the small sun, and touched it. The paint shifted. It was so fresh that it hadn’t even bled into the fibers of the paper. Paint, paper, conservation glue—all were of about the same vintage, going back two years at most.

Gimpel had been conned.

Zagel was curious about the labels on the hardboard, which bore the names of various galleries and collectors dating back several decades and were brown with age. Labels are generally made of cheap paper with a high acidity; after a few years they turn brittle and scratch easily. Zagel moved her finger along the surface of the Nicholson labels and felt a cottony, elastic surface. They were brand-new. When she wiped them with a kitchen sponge, the dark brown color washed off. She guessed that they had been soaked in tea or coffee. Whoever had forged the painting had also tried to fake the provenance.

It had been Zagel’s experience that dealers could turn nasty when a painting’s authenticity was questioned, but she didn’t hesitate to give Gimpel the bad news. She had known him for years and respected his erudition and integrity.

“The Nicholson’s a fake,” she told him. “I’m sorry.”

He had paid £18,000 for it, and Zagel decided not to charge him for her work. She told him she hoped he’d get his money back. It wasn’t a very good forgery, she said, but a lot of effort had gone into it. The tacks, the labels, the false backing—even the visible pencil marks that Nicholson often left on his work—were clear signs that the forger had done his research. In fact, he had taken so much trouble with it that Zagel was sure it wasn’t a one-off; there must be other similar works on the market.

Gimpel took note. Forgeries were part of the risk of doing business. They often changed hands in the shadowy parts of the art world when a new buyer tried to fob off a suspected dud on the next unwitting collector. Ironically, the longer a fake circulated and the more owners it had had, the more authentic it appeared to be. Coincidentally, Gimpel had been working on the reissue of his grandfather’s Diary of an Art Dealer and had just come across a reference to a counterfeit in an entry dated March 12, 1918: “A fake Gainsborough, a Blue Boy, has just been knocked down [sold] at the Hearn sale in New York for more than $32,000. It’s harder to sell a genuine painting.”

Every generation had its fakes, Gimpel thought. Little did he know that this one would play an important role in one of the great forgery trials of the century.

Bartos readily agreed to the Korean’s demand. He made copies of the provenance material, removed the transparency of Standing Nude, 1955 from his files, and sent it all to the Giacometti Association by courier, along with a letter offering the work for inclusion in the forthcoming catalogue raisonné.

He fully expected a prompt response, and then the deal would be a snap.