From the moment it was created in 1879, a tiny landscape of the River Seine by Pierre-Auguste Renoir has been characterized by a tangled weave of embellishments, layers and knots.

When the Impressionist master sat down to dash off a quick oil sketch of the River Seine, he picked up not the usual piece of canvas, but – museum experts confirmed Thursday – a linen napkin with an elaborate geometric pattern in which threads twist above, below and around one another.

"Our textile curator, Anita Jones, spent a lot of time looking at the painting under a high-powered microscope," Katy Rothkopf, the museum's senior curator of European painting and sculpture, told reporters gathered for the press preview of a new exhibit, "The Renoir Returns," which opens Sunday.

"The fabric is a type of linen damask that in the late 19th century was used for table linens," Rothkopf said. "It was unusual for painters to use this type of fabric, but it turned out to be a good choice. Linen increases in strength when wet and is smoother than wool or cotton."

But as elaborate as the fabric's geometric structure is, it's virtually a model of simplicity when compared to the 135-year-old artwork's past.

The FBI announced on Thursday that the investigation into the theft of "Paysage Bord du Seine" from the museum in 1951 has been closed. After interviewing dozens of witnesses over nearly 18 months, there isn't sufficient evidence to arrest anyone either for stealing the artwork or for intentionally possessing stolen property, Special Agent Gregg Horner said.

"A lot of people are disappointed when these investigations end without a prosecution," Horner said in an interview at the FBI's Baltimore branch. "But, sometimes that's the nature of these cases. The woman who was in possession of the painting wasn't even born then, so she obviously didn't steal it. And, we had no indication that she knew that it was stolen property."

It all makes for an irresistibly romantic story expected to draw throngs of visitors to the museum this weekend when the Renoir goes on display for the first time in more than six decades, as part of an exhibition drawn from the collection of the painting's donor, the Baltimore heiress and philanthropist Saidie May.

Part of the painting's allure is that it has consistently passed through the hands of women with vivid personalities. They include May, who bought that water view from a Paris gallery in 1925 and later bequeathed it to the museum.

The twice-divorced May was a free spirit, an amateur artist and a cousin of the art collectors Etta and Claribel Cone. (Two paintings by May herself also are on display in the exhibit.) It was May who put up the money that enabled the artists Marc Chagall and Andre Masson to flee from Nazi-occupied France during World War II and to escape to America with their families.

More recently, the Renoir was in the possession of a Virginia driving instructor named Marcia "Martha" Fuqua. She made headlines worldwide in September, 2012, when she said she'd bought a Renoir painting at the Harpers Ferry Flea Market as part of a box of odds and ends costing $7 without knowing the artwork's true value.

The 52-year-old Fuqua announced plans to sell the painting at auction, where it was expected to fetch as much as $100,000. But the day before the painting was to go under the gavel, museum officials uncovered documents indicating that the artwork had been stolen in 1951.

The sale was called off, the FBI seized the artwork, and Horner began trying to track down the thief.

Fuqua's brother, Owen Maddox "Matt" Fuqua, has publicly cast doubt on his sister's account of buying the artwork at a flea market — though he later admitted in a deposition that he had lied when he claimed to have seen the painting in the Great Falls, Va., home of his late mother, Marcia Fouquet.

Horner said he talked to witnesses who think they saw the painting in Fouquet's home, and others who believe they glimpsed Fuqua buying it at the flea market. He identified former museum staff members, contractors and exhibitors who had access to the museum when the painting was stolen (including a former friend of Fouquet's) and, when possible, interviewed them.

"There were so many different stories," Horner said, "it made it tough to get to the bottom of things."

The agent's one meeting with Fouquet also shed no light on the landscape's history.

"I did not ask her about the Renoir," Horner said. "I did not feel that the timing was right. She's a very interesting lady, very well-educated. We had a nice, pleasant conversation. I talked to her in general terms about her art."

He considered returning to conduct further interviews, but decided against it because of the rapid decline in Fouquet's health.

"Given her illness," Horner said, "I didn't think it was appropriate."