The mysterious case of Reza Zarrab, a Turkish-Iranian businessman facing federal charges in New York, has grown even stranger over the past couple of weeks.

Zarrab, who is thirty-three, was arrested by F.B.I. agents, in Miami, last March. At the time, he was one of the flashiest and wealthiest businessmen in Turkey. He sported a pouf of black hair; owned twenty houses, seven yachts, and a private jet; was married to one of Turkey’s biggest pop stars; and counted among his friends Recep Tayyip Erdoğan, Turkey’s strongman President.

The U.S. government, however, believes that Zarrab masterminded a sprawling operation to help the Iranian government evade economic sanctions that were put in place to hinder the country’s nuclear-weapons program. Zarrab’s operation—which relied on what the Turkish government claimed was a legal loophole in the sanctions—involved shipping gold to Iran in exchange for oil and natural gas, which Zarrab then sold. The scheme, according to prosecutors in New York’s Southern District, involved moving enormous amounts of cash, gas, and gold; at the operation’s peak—around 2012—Zarrab was buying a metric ton of gold and shipping it to Iran every day. The Obama Administration protested Zarrab’s operation, which the media dubbed “gas for gold,’’ but he carried on anyway. For the Iranians, the gold was as good as American cash, and it helped shore up the rial, Iran’s currency, whose value was collapsing.

Since last March, Zarrab has been sitting in the Metropolitan Correctional Center, in Manhattan, awaiting trial. The questions—and conspiracy theories—about him and his case, meanwhile, have only multiplied. At the time of his arrest, Zarrab was more or less living under the protection of the Turkish government, and he had every reason to believe that the U.S. government was after him. Why, then, did he fly to Miami? Zarrab told agents that he was on a family trip to Disney World. But many Turks who follow the case believe that Zarrab flew to the United States in an attempt to strike a deal with American prosecutors.

Why would he do that? It’s not clear if any deal was ever discussed, but Zarrab is probably in possession of enough evidence to implicate several senior members of Turkey’s government, whom American prosecutors say Zarrab was bribing so that he could carry on with his scheme. Zarrab, prosecutors have told a federal judge in New York, used “his tremendous wealth not only to purchase several homes, yachts and other assets, but also to buy access to corrupt politicians in Turkey.”

Zarrab’s far-flung activities first came to public light four years ago—entirely by accident. On January 1, 2013, a cargo plane from Accra, Ghana, was diverted to Istanbul’s main international airport, because of fog. When customs officials searched the plane, they found three thousand pounds of gold bars. Turkish prosecutors—who at that time still had enough independence to challenge the central government—determined that Zarrab had been paying millions of dollars in bribes to senior officials in Erdoğan’s government, and they had the businessman arrested and charged. The police themselves were stunned. “We didn’t expect this little investigation to give way to a bigger one,’’ Nazmi Ardıç, the chief of the Istanbul police department’s organized-crime unit, told me in 2015.

According to documents filed in U.S. District Court in Manhattan, the Minister for the Economy, Zafer Çağlayan, accepted more than forty-five million dollars in cash, gems, and luxury goods from Zarrab. When police entered the home of Süleyman Aslan—the C.E.O. of Halk Bank, which Zarrab allegedly used to launder his money—they found shoeboxes stuffed with four and a half million dollars. (Both Çağlayan and Aslan have denied any wrongdoing.) Wiretapped phone conversations also appeared to implicate members of Erdoğan’s family.

The cargo-plane incident and subsequent investigation of Zarrab roiled Turkish politics. Erdoğan, instead of backing down, accused Fethullah Gülen, an imam and former ally living in exile in the Poconos, in Pennsylvania, of trying to mount a coup against him. It was then that Erdoğan initiated the first in a series of purges across the Turkish government, firing, transferring, or jailing thousands of police officers and prosecutors. Afterward, the charges against Zarrab were dropped, and he was released from prison. The power struggle between Erdoğan and Gülen climaxed last summer, when followers of Gülen inside the Turkish military took part in a real attempted coup against Erdoğan’s government. Erdoğan beat back the uprising, but not before more than two hundred and sixty people were killed. Since then, Erdoğan has been busy arresting and detaining anyone linked to the country’s democratic opposition, and many people who are not.

Zarrab’s arrest in the U.S. occurred a few months before the attempted coup. Since then, Erdoğan has tried to have Zarrab sprung; last year, his government asked Loretta Lynch, then the U.S. Attorney General, to release him, and Erdoğan himself raised the issue last September in a meeting with Joe Biden, then the Vice-President. Erdoğan even accused the U.S. Attorney who indicted Zarrab, Preet Bharara, as well as the judge overseeing the case, Richard Berman, of having links to Gülen, whom Erdoğan describes as a “terrorist.” Bharara and Berman, Erdoğan charged, had been “wined and dined” by Gülen’s organization.

Why does Erdoğan care so much about Zarrab? It could be that Erdoğan is just a loyal friend. But the evidence found by Turkish prosecutors in the original case against Zarrab suggests that Erdoğan himself, or his family, could be tied to Zarrab’s scheme. Perhaps Erdoğan is afraid that Zarrab, facing decades in prison, will eventually talk.

After his arrest, in Miami, Zarrab hired some of the most expensive lawyers in New York. They tried to secure a comfortable bail arrangement—and failed. They then sought to have the case thrown out entirely, and failed at that, too. For a time, it looked as though the Zarrab case was headed for trial. Then, last month, came several dramatic developments. Zarrab fired most of his lawyers and hired Rudy Giuliani, a confidant of President Trump, and Michael Mukasey, the former U.S. Attorney General. Then Trump fired Bharara, the prosecutor who indicted Zarrab in the first place. With a legal team friendly to the President in place, and a hostile prosecutor out of the way, Zarrab may be hoping for a sweet deal from the prosecution. It has since been revealed that Giuliani and Mukasey travelled to Turkey in February to meet with Erdoğan about the case—another of Zarrab’s lawyers said that they were seeking a “diplomatic solution” to the situation. Berman, the judge, has asked that Giuliani and Mukasey provide more information about their role in the case.

Finally, another new layer of mystery: last month, F.B.I. agents arrested Mehmet Hakan Atilla, the deputy C.E.O. of Halk Bank—the same bank that prosecutors allege that Zarrab used to launder his gas-for-gold transactions—upon his arrival at J.F.K. International Airport, in New York. The case against Atilla was built on much of the same evidence—wiretapped phone conversations—that was used to charge Zarrab. (On Thursday, Atilla pleaded not guilty to the charges against him.) What was going on? Would Atilla simply fly to J.F.K. without a care, even though his former client had been arrested a year earlier in a very public case? Or was something murkier at work?

The Turkish government was not happy with Atilla’s arrest; Halk Bank is one of the largest financial institutions in the country. As with almost everything that goes wrong in Turkey these days, the country’s leaders are blaming Gülen, the exiled imam in the Poconos. “The move against Halk Bank’s Atilla,’’ Binali Yıldırım, the Turkish Prime Minister, said, “is another plan and trick of the Gülen movement.”