In this mystery, there are the makings of an Umberto Eco novel: century-old letters, musty archives, an Italian art dealer, a village priest, a 19th-century Venetian railway sticker, a teenage boy fleeing Nazis. The center of this tangled arcanum? A frame. As one might guess, it is no ordinary frame.

It is a gold leaf Italian Renaissance altar frame with carvings of pears, palmettos and acanthus leaves. It is grand, measuring 16 feet high and 12 feet wide. "The story of this frame could fill up a novel," says Martin Stiglio, director of the cultural office of the Italian government in Washington. "It has been on adventures."

This specimen is also a rather extravagant example of a rather quiet revolution in the art world that has placed increased importance and value on reuniting artworks with their original frames. For the past 11 years, it has hung in the studio of frame historian and conservator William B. Adair on 22nd Street NW. This week it is returning to Italy, reversing a long-standing tradition of art and antiquities heading in the other direction. It is being reunited with the Santa Maria delle Grazie church in Cortemaggiore, a sleepy farming town southwest of Venice that housed it 500 years ago. Joining it will be nine of 11 of the 15th-century painted panels for which the frame was made.

"It's exceedingly rare that a frame should be saved and that it should be returned by owners in England and America to the original church in Italy," says David Alan Brown, curator of Italian Renaissance paintings at the National Gallery of Art. "I think it's a real cause for celebration."

The frame is for a polyptych, which means it has openings for more than three paintings. In this case, there are 11 openings. Frames of this size were common in Renaissance Europe, but few remain.

"It's rare for a polyptych frame to survive. With most polyptychs, when a church sold it, it was cut up and sold as separate pieces. There are two reasons. It's easier to move around in smaller sections, and second of all, you can usually make more money from selling things individually than from selling the whole thing," says Mark Leonard, chief conservator of paintings at the J. Paul Getty Museum in Los Angeles. "It's just a great story. Absolutely extraordinary. And fascinating."

The frame's owner is an 83-year-old British framemaker named Paul Levi, and the story begins with him. Levi, a German Jew, fled the Nazis at 15 for London. At war's end, the British mistakenly expelled him and interned him in a camp in Canada. There, to avoid living among the hostile German internees, he managed to flee again, this time to the Italian internment camp nearby. The Italians nurtured him, and "since then, he has had a special place in his heart for Italians," says Stiglio. (Eventually, the British realized their error and Levi returned to London.)

"I would have liked perhaps to study art history, but that was completely impossible," Levi said in a telephone interview from London. "So I became a framemaker. I also had an interest in the history of frames."

He often puttered about flea markets and junk sales, looking for antique frames. One day in 1963, he happened upon the altar frame.

"What you have to imagine is that this thing was all in pieces and stacked like building board," Levi said. "I couldn't see all of the frame, but the decoration on the frame I could see was about 1480. I was a framemaker and interested in frames -- it was my obligation to buy it."

He paid 250 pounds. But he had neither a studio large enough to reassemble it nor time to devote to researching its past. Three decades later, in 1991, he was retired and discovered the frame anew. He sent it to Adair, a frame conservator at the National Portrait Gallery who had struck out on his own in 1982 and become a well-known "frame finder," an astute tracker of period frames for museums.

"All I had to go on was there was a railway station sticker on the back of one of the pieces that said 'Veneto,' " says Adair. Years of research throughout Italy by phone and fax led nowhere. Rather than have the frame languish unseen in his studio, Adair approached the National Gallery, Washington National Cathedral and others to see if they might be interested in buying it. The National Gallery considered it for a work of Venetian Renaissance painter Giovanni Bellini, but decided its decoration was not religious enough. The National Cathedral considered it for a chapel, but opted instead for a plexiglass sculpture of praying hands.

In the summer of 2000, Adair remembered that inside the crates the frame had been sold in was an antique furniture knob. Levi told him he believed the knob was from the Victoria and Albert Museum. Could the frame have been through the Victoria and Albert, too? Adair also had come upon a 19th-century book on frames by Sir John Charles Robinson. He learned that Robinson had worked at the Victoria and Albert (then the New Kensington Museum) in the last quarter of the 19th century. Such a frame connoisseur might have wanted the museum to purchase this one. Adair sent his daughter, Annie Gronchi, and a young curator named Jennifer Janicki to London.

The two camped in the museum's basement and began looking through acquisition books, beginning with 1875. There were thousands of purchases listed, and hundreds of frames. Janicki hoped that the 16-by-12-foot dimensions would be unusual enough to be mentioned in the index. She was right. On the third day, in the 1884 book, she found an entry for a 16-by-12 frame.

"I was sitting at a table, and you don't talk, you don't move in these musty archives in the basement. When I saw it, I got dizzy and started to stand up. But when I saw everyone quietly over their books, I sat back down. I wanted to scream, 'I found it!' " Janicki remembers.

Janicki perused the original correspondence about the frame's purchase. "The paintings are by Filippo Mazzuoli, father of the great painter Parmigianino. The date is 1490," wrote Antonio Marcato, the Venetian dealer who sold the piece to the Brits. An unsigned handwritten note said the frame might have come from "the church of S. Lorenzo (or S. Maria delle Grazie) at Cortemaggiore near Piacenza." Mazzuoli, who is more often referred to as Mazzola (c. 1460-1505), was a less than major artist whose work is in the Walters Art Museum in Baltimore, among other international collections.

Janicki and Gronchi flew to Venice and drove into the Emilia-Romagna region west of the city. The church of Santa Maria delle Grazie was a fortresslike medieval edifice with few and narrow windows. Gronchi looked in vain for the church's priest. She called her father on her cell phone and said, "Dad, I'm in the church and found no paintings that corresponded to the size. However, there are some smaller paintings in Gothic frames over the doorways to the sacristy. What should I do now?" Adair recalls. "I told her, 'Don't give up now, keep asking questions.' "

The priest's mother was in the sacristy. She was not friendly. She could not understand what frame Gronchi could be talking about. She seemed to think she was trying to steal paintings. Gronchi left, stymied. But she went to a tobacco shop next door to get some things for the ride back. The clerk asked her what she was doing in town. When she told him, "He exclaimed, 'The paintings you seek are in the National Museum in Parma, and my good friend Edigio Bandini, the photographer, documented them before the museum took them for safekeeping!' " says Adair.

Janicki and Gronchi went to Parma, and told curator Davide Gasparotto their story. He confirmed that the polyptych frame once held nine paintings in the museum and all had come from Santa Maria delle Grazie. Each oil-on-wood panel featured a saint, and among them was the conversion of Saint Paul. The frame's gilt and indigo blue gesso highlighted the luminous figures.

The church, in the middle of prolonged hostilities during the wars for Italian independence in the mid-19th century, had been forced to close. Like many churches in Northern Italy, it sold the frame and its paintings to raise money to reopen. There were two other paintings that were not in Italy. One was in the Hungarian National Museum in Budapest. The other was presumed to be in France. Levi, hearing that the frame's home had been found, offered to donate it to the church. Adair donated his conservation of the frame, which has taken more than a year. The museum agreed to return the paintings to the church. And while the priest's mother was suspicious at first, her son, after learning of Levi's gift, talked of spearheading a campaign to build a statue to Levi in the town square.

Stiglio, the Italian cultural attache, says the priest was thrilled to have such an important piece coming to his church. "He woke me up quite a few times in the middle of the night. He started immediately to understand how important it would be for his church to have this piece and put it together. He was able to find money not only to pay for the transportation of this frame back to Italy but to make sure new microclimate controls will protect it and the paintings."

To thank Levi, the Italian government knighted him. Next year, Mazzola's son, Parmigianino, is slated to be the subject of a major international exhibition in Vienna and Parma in honor of the 500th anniversary of his birth. "So it's an appropriate moment to return the frame to Cortemaggiore, at this moment when Mazzola's son is being celebrated with these big exhibitions," says the National Gallery's Brown.

No one knows who made the frame itself, but it was most likely a team that worked closely with the artist and the church. "It's a very fine example of Italian craftsmanship," says Brown. "It gives us a rare glimpse into what these ensembles looked like at the time. The decoration is classical, it's the new Renaissance style of ornamental rather than Gothic."

"It's unusual in so many areas, but particularly that something this important is being reunited with its church and its paintings. It's such a great, great tale," says Eli Wilner, a New York frame conservationist. "I've reunited 19th-century frames with their paintings, but nothing like this. This is monumental."

A portion of the 12-by-16-foot Renaissance altar frame will be reunited with nine of its 11 painted panels in its original church in rural Italy.Conservator William Adair theorized the Italian altar frame had gone through the Victoria and Albert Museum, speculation proved by the research of curator Jennifer Janicki.