The International Banking Corporation, in Bahrain, generated billions of dollars while issuing a series of fake loans. Illustration by Shout

When Glenn Stewart enrolled at the University of Oxford, in 1975, he was not a typical first-year student: a twenty-year-old American with mediocre grades, he had taken neither A-level exams nor Oxford’s entrance test. But he had an unusual degree of confidence, and, after securing a strong reference from an English grammar school that he’d attended for a year, he persuaded an Oxford admissions officer to let him in.

Stewart had grown up in the Washington, D.C., suburb of College Park, Maryland, where his father taught chemistry at the University of Maryland. An enterprising kid, he made money on weekends by selling soda in the bleachers at college football games. After Stewart’s junior year in high school, his father went to England on sabbatical and took the family along. As Stewart later wrote in a self-published memoir, “A Gentleman and a Player,” he loved being among foreigners: “I could tell they were bemused by my brashness, never having met a Yank up close before.” After a year at the grammar school, he reluctantly followed his family back home, received his diploma, and completed a couple of semesters at the University of Maryland. America bored him, however, and he sought his fortunes abroad.

At Oxford, Stewart, who was tall and lean, with long brown hair, exuded what one classmate called a “sense of adventure.” He joined a clique of theatre enthusiasts who included Rowan Atkinson, of “Mr. Bean,” and Pierre Audi, a student from Lebanon, who now directs the Dutch National Opera. Audi told me that Stewart had seemed unusually attuned to other cultures. The tumult in the Middle East—the Yom Kippur War, the opec oil embargo—made a strong impression on Stewart. Where others saw a crisis, he glimpsed opportunity. He began intensive study of Arabic and Islamic history. His thesis explored Byzantine-Hamdanid relations in the tenth century and the evolution of the Christian concept of holy war. While Audi was trying to “run away from the Middle East,” he told me, Stewart was charging toward it.

Stewart graduated in 1978. He wanted to pursue a career in intelligence, but the C.I.A. rejected his application. He fantasized about a life in the theatre, but, as he told me not long ago, he decided that “the best thing to do was to go and try to make money first.” He passed the C.P.A. exam and worked briefly as an accountant in San Francisco, where he dated a colleague, Donna Gannon. They married, and in 1983 they moved to Saudi Arabia after he took a job in Khobar, a drab city on the Gulf coast which anchors the country’s oil industry.

After two years, he and Donna moved twenty miles east of Khobar, to the island kingdom of Bahrain. They had two sons. In Bahrain, most Westerners lived in gated compounds, but Stewart and his family rented an apartment in a predominantly Arab neighborhood. Compared with Saudi Arabia, he told me, Bahrain was freewheeling—“really open, with bars in hotels and restaurants.”

In 1989, Stewart got a job with a wealthy Saudi family from Khobar, the Gosaibis. They had made billions of dollars by investing in real estate; by bottling and distributing Pepsi; and by selling steel piping to Saudi Aramco, the national oil-and-natural-gas behemoth. The family business was known as AHAB—the Ahmad Hamad al-Gosaibi Brothers. In the eighties, AHAB had opened a trading house and an investment company in the capital of Bahrain, Manama, which became an Arab financial hub after civil war in Lebanon diminished the allure of Beirut.

Stewart worked at the Gosaibis’ trading and investment companies, specializing in commodities deals and in Islamic finance, which prohibits the sale of debt and the collection of interest on debt. After several years, he developed a relationship with Maan al-Sanea, a son-in-law of the Gosaibis, who was one of the more dynamic executives in the family business. According to Brooks Wrampelmeier, a retired U.S. diplomat who served as consul-general in the Saudi city of Dhahran, the Gosaibis were “traditional types,” but Sanea, who was in his mid-thirties, was a bold entrepreneur, eager to explore “new ways in which money could be moved.”

Over time, Stewart earned Sanea’s trust. “As I performed, he had more confidence in me,” Stewart said. “My job was to raise money and loan facilities, and I did it very effectively.” Their partnership was soon making an astonishing amount of money. But according to a corporate-investigation firm, a team of forensic accountants, and a law firm in Washington, D.C., hired by the Gosaibis, their success wasn’t entirely a reflection of financial skill. Stewart and Sanea, they contend, presided over a business, the International Banking Corporation (T.I.B.C.), that perpetrated a multibillion-dollar fraud—and then left the Gosaibis with the bill.

Stewart and Sanea strongly deny any wrongdoing, and say that ultimate financial responsibility lies with the Gosaibis. (A headline in the Wall Street Journal has characterized the dispute as a “saudi family feud.”) The scandal has inspired litigation in ten countries, with several cases still ongoing. But one thing seems clear: T.I.B.C. issued a series of fake loans, and in 2009 it imploded in spectacular fashion, triggering the largest corporate default in the history of the Middle East.

In the nineteen-seventies, three Gosaibi brothers—Suleiman, Abdulaziz, and Ahmad—oversaw the family business. Abdulaziz, the middle brother, “masterminded the company’s growth,” Michael Field wrote, in a chapter devoted to the Gosaibis in his 1984 book, “The Merchants: The Big Business Families of Saudi Arabia and the Gulf States.” Abdulaziz had five daughters and a son. In 1980, one of his daughters married a distant relative from Kuwait: Maan al-Sanea. His family lived comfortably, but compared with the Gosaibis its assets were modest; years later, he presented himself in a corporate pamphlet as a “self-made man.” Sanea, who had received combat training from the Kuwaiti Air Force, was self-assured, and he arrived at his wedding in a red Rolls-Royce. A family member who attended the wedding told the Wall Street Journal that other guests considered this “a bit unseemly.”

Abdulaziz’s only son, Saud, lacked Sanea’s poise and command, and Abdulaziz treated Sanea like his own child. Their closeness caused resentment. Later, in a deposition, one of Sanea’s in-laws contended that Sanea “was not liked” by some of the Gosaibis; Sanea, in a court filing, acknowledged the friction and recalled that, during a dispute over office space, a Gosaibi relative had once “put a gun to my head.” (No one in the Gosaibi family agreed to be interviewed for this article.)

In 1981, Abdulaziz asked Sanea to run the Money Exchange—a business, based in Khobar, that gave expatriate workers a convenient way to send wages home, and offered a few basic financial services. The Money Exchange also functioned as an in-house bank for the Gosaibi family, whose members could withdraw funds to cover personal expenses and to support other AHAB enterprises. Sanea was determined to expand the Money Exchange, and an ad was placed in the Financial Times promoting its capacity to provide “a wide range of financial services.” Over the next two decades, the business grew significantly. Sanea was a controlling boss—he liked to be called Sheikh Maan—and he strictly supervised communication, especially when it concerned the Gosaibis; in 2004, he issued a memo declaring that “all mail and or correspondence addressed to Uncle Suleiman or Saud al-Gosaibi should be forwarded to my office for my review first.”