Written by Susannah Palk, for CNN

Five artworks from the Dutch Golden Age are finally returning to their rightful place, more than a decade after they disappeared into the shadowy depths of the illicit art market.

The works belong to the Westfries Museum , located in the Dutch maritime town of Hoorn, where they will be unveiled on October 7 -- a far cry from Ukraine, where the paintings were uncovered.

A new deal

In January 2005, thieves are thought to have hidden inside a coffin on display inside the museum before disabling the security system and taking off with 24 paintings and 70 pieces of silverware. It was the bulk of the museum's 17th and 18th century collection, worth approximately 1.3 million euros ($1.45 million).

With no solid leads, it was feared the paintings would never be traced. But in July 2015, the museum's director, Ad Geerdink, received word that someone from a Ukrainian militia force, a man named Borys Humeniuk, had made contact with the Dutch embassy in Kiev.

A deputy commander from the Organization of Ukrainian Nationalists, Humeniuk claimed to have found the paintings, and said he was willing to hand them over.

"He said his battalion had found all 24 painting in a villa belonging to former president Viktor Yanukovych while fighting Russian separatists in the east of the country," claimed Geerdink.























1 / 12 In 1911, Leonardo Da Vinci's "Mona Lisa" was stolen from the Louvre by an Italian who had been a handyman for the museum. The now-iconic painting was recovered two years later. Credit: JEAN-PIERRE MULLER/AFP/Getty Images

It was now a question of what Humeniuk wanted in return. At this point, the museum enlisted the help of Dutch art historian and art crime investigator Arthur Brand.

From the start Brand knew the issue would be money.

"If you have stolen paintings in your possession, of course you can ask for a reward," said Brand. "But if you ask, you have to accept the reward that is there. If you do not, then you're engaging in a criminal act."

Meeting in Kiev -- and armed with official valuations -- Brand told Humeniuk that in its badly damaged state, the entire collection was worth not millions, but around 500,000 euros ($560,000), and offered a finders fee of 50,000 euros ($56,000).

"Humeniuk said he would talk with his soldiers, but I saw in his eyes that it was the end of any deal," said Brand.

An illegal art market

With 15 years of experience in the illicit art trade, not much surprises Brand anymore. He's recovered well over 200 works of art, including ancient Aztec artifacts, antique porcelain plates and numerous paintings looted by the Nazis.

In one of his most high profile cases, Brand aided German police in the retrieval of a pair of bronze horse sculptures by Josef Thorak that once belonged to Adolf Hitler.

According to Interpol, it's almost impossible to put a financial figure on the illicit art trade, although the FBI and the US Department of Justice have called it the third highest-grossing criminal trade in the world after drugs and arms.

Brand himself estimates the illegal art market's value to be around 8 billion euros ($8.9 billion) a year.

Westfries Museum director Ad Geerdink, pictured next to the painting "Lady World" in Kiev, Ukraine. Credit: Westfries Museum

"The amount of illegal activity in the art world is horrible, and I believe 30 percent of what is being offered is fake," he said.

Despite this, Brand often finds criminals in possession of stolen art works are just as keen to be rid of them as he is to retrieve them.

"In many cases, the art is used as a payment or as security in the criminal world and pieces get passed around, changing hands frequently," said Brand.

"If criminals get caught with these stolen goods, they will be arrested and face jail time. (The artworks are) evidence, so often they're destroyed. We've seen this happen many times."

In one of his most recent cases, Brand helped recover a Salvador Dali and a Tamara de Lempicka stolen from the now-closed Dutch Scheringa Museum of Realist Art in 2009. He says the paintings changed hands three times in the eight months he was on the case,

"It's not good for the paintings. They get damaged and, secondly, it's almost impossible to work out who the original thieves are. Just forget about finding the original thieves and concentrate on getting the paintings back."

Repatriated paintings

Back in Ukraine, the fear for the Dutch paintings was not destruction, but yet another change of hands, with some of the paintings being offered for sale on the black market.

In April 2016, after notifying Dutch police and the Ukrainian authorities, the Ukrainian Foreign Minister Pavlo Klimkin announced the recovery of four paintings in a special operation by the Ukrainian Security Service. A week later, thanks to one of Brand's Ukrainian sources, a fifth painting was also unearthed.

While only five of the 24 paintings have been retrieved, Brand says he's confident the remaining 19 paintings will eventually be returned.

"We will get them back, sooner or later. They cannot sell them anymore; the images have been seen from New York to Japan, and we're on their track. We won't give up."

Back in Hoorn, the town is eagerly awaiting their return.

"We are very emotional about this theft," says museum director Ad Geerdink. "A part of our history was stolen, a part of our cultural heritage. Now five lost sons of Hoorn will return, and it's going to be a very special day."