AMSTERDAM — “Borys is a sympathetic crook,” says Arthur Brand, an art recovery expert whose business has led to encounters with all sorts of criminals. But, he cautions, “Guys like that are kind of Jekyll and Hyde.”

And Borys, full name Borys Humeniuk, is in Ukraine, where he’s hooked up with some folks who are definitely on the Hyde side in a true tale of art theft, Old Masters, new militias, secret services, and arms purchases.

In a meeting that took place on Aug. 4 at an office right next door to the Dutch embassy in the Ukrainian capital, Kiev, the Dutch Westfries Museum was offered a chance to buy back 24 paintings stolen in 2005.

Humeniuk was there to broker the deal, and as soon as Brand saw him—heavy-set, square headed, with penetrating light brown eyes—he thought, “This is someone you would not like to encounter on the battlefield.”

Humeniuk styles himself a soldier-poet, and was deputy commander of the OUN, or Organization of Ukrainian Nationalists. The group is named after the infamous ultranationalist military movement known for helping the Nazis, then fighting them, during World War II, and in the meantime slaughtering tens of thousands of Jews and Poles.

In current-day Ukrainian politics, this new OUN is involved in the armed struggle against the Moscow-backed Ukrainian separatists in the east of the country, where Humeniuk has complained publicly about the lack of military supplies from the government, and is often linked to the extremist Svoboda party. Humeniuk, who according to the OUN was recently fired from its ranks, now appears on the political list for Svoboda.

The art that Humeniuk was trying to flog consists of two dozen 17th and 18th century paintings depicting traditional Dutch landscapes, portraits and Biblical scenes stolen, along with a large collection of silver, on the night of Jan. 9, 2005, from the museum in Hoorn, less than an hour’s drive north of Amsterdam.

Among the paintings were “Rebecca and Eliezer” by Jan Linsens and the rather bawdy and baroque “Lady World” by Jacob Waben.

Art theft expert Brand traveled to the region to investigate the case. “The museum asked me to handle the talks over the collection of artworks,” Brand says. “Before the meeting I looked into whom I was meeting, this Borys Humeniuk, a pretty heavy guy. When I saw him first, I must admit, there was part of me that liked him.”

A month earlier, Humeniuk had approached the Dutch embassy in Kiev. He said the ultranationalist militia had found the collection of paintings in a villa belonging to some sympathizers of ousted Prime Minister Viktor Yanukovych. But Brand gives little credence to that version of events.

Stolen art is often used in ideals among criminals, sometimes for barter, sometimes as collateral, and may change hands several times in the process. Inevitably those who try to ransom it claim they found it by accident, or, as the mob in the U.S. likes to say, “it fell off the back of a truck.” There is no indication thus far who the original thieves might have been.

In the initial contacts, in July, an email was sent to the museum with a photograph of one of the paintings and a new newspaper next to it (much like photos of humans held hostage). The people who had the art claimed they just wanted to return it to the Netherlands and only asked for “a little compensation for the expenses,” says Brand. “But it also said they thought the collection was worth €50 million. So I predicted they just wanted money. In these circumstances a 10 percent ‘finders fee’ is common, so I said, ‘They will ask for €5 million.’ Which is what they did.”

Brand had no intention of paying that much. By the museum’s estimate, the artwork, valued at around €1.3 million ($1.42 million) before the robbery, was now worth no more than about €500,000 because of the extensive damage caused when the robbers cut the paintings out of their frames and shipped them abroad. Brand would offer no more than €50,000 in the name of the museum.

“I understand now that they’re worth much less, but I will have a hard time convincing the people who assigned me to accept that,” Humeniuk told him. It was then Brand realized he was not dealing with the man in charge. Brand says that after using his extensive network the trail leads directly to two much more prominent Ukrainian figures: Oleg Tyahnybok, a former parliamentarian who is the leader of the anti-semitic Svoboda movement, and Valentyn Nalyvaichenko, former head of the SBU, the Ukrainian secret service.

A Ukrainian politician with ties to the militia of volunteers told Brand the museum wasn’t seen as the rightful proprietor but as just another interested party. That contact was also the one who told Brand the man behind the deal was Tyahnybok.

Brand knew the €50,000 would be unacceptable for whoever sent Humeniuk, and it was. “The next step for them would be to keep us dangling and bargain with other parties at the same time” Brand told The Daily Beast. “Via our network of informants we found they were trying to sell them in the Ukraine, to German criminals, and in Tadjikistan.”

Now that the deal has gone sour, the thieves are trying to sell the art on the black market, and the museum is going all out to publicize the case in the hopes that will make it more difficult for them.

Museum Director Ad Geerdink has made a public appeal, urging Ukrainians to help with the restitution of the paintings to their rightful place. “They’re not assets you trade for some lousy money,” he says in a YouTube clip addressing the Ukrainians. “These pieces of art are part of our cultural heritage, our history, and they belong here.”In the meantime, Brand says he’s received confirmation from the Ukrainian authorities that Oleh Tyahnybok is in fact involved. When asked about the case by the local press, Ukrainian minister of Internal Affairs Arsen Avakov says he is in touch with the Dutch authorities, but declines to comment further.

Valentin Nalyvaichenko remains much more elusive. Brand says, “All the indications of his involvement are there; he’s the former head of intelligence, his name surfaced several times and he is close to Oleh Tyahnybok, but legally we need to be able to substantiate further.”

Being accused of taking part in a criminal deal over national treasure clearly hasn’t dampened Oleg Tyahnybok’s spirit one bit. On his Facebook page the extremist leader taunts: “Dear representatives of the West Frysian Museum,” it says in the comment with a photo in which he’s seen smiling and gesturing at a portrait of Stepan Bandera, one of the founders of the OUN: “Here, come and get your ‘found’ paintings and display them.”