Rajaratnam heard them out but fixated on another idea. He persuaded them to help create a highly leveraged vehicle, with money from investment banks, that would invest in a smattering of funds and strategies, some run by Galleon and some run by Trehan’s firm, BroadStreet Group. The three partners would call their new entity Voyager Capital. But as Rajaratnam and Trehan focused on the nuts and bolts of Voyager, Gupta seemed taken with more grandiose concepts, like turning the fund into a platform on which to build an Asian merchant-banking business. It soon became clear that the former management-company C.E.O. wasn’t comfortable with the minute financial details that are essential to investors risking hundreds of millions of dollars on the markets.

From the start, Voyager was a project of Rajaratnam’s power. He put in $40 million, giving him an 80 percent stake in Voyager. Trehan, whose firm was behind Voyager’s clever structuring and generous credit terms, put up $5 million for a 10 percent stake. Gupta also put in $5 million. Gupta was originally supposed to receive a share of profits depending on the value that he brought through his connections. But Rajaratnam signaled that those connections were less valuable than his deep pockets. “What do I need him for?” he told Trehan.

Voyager was an instant success. By early 2006, three months after it was set up, shareholder equity rose to $58 million, a return of nearly 17 percent. But Rajaratnam began managing the fund as if it were his own, steering it to invest in Galleon’s funds rather than BroadStreet’s, reaping more of the management profits for himself. Trehan was livid. That March, Gupta and Trehan made their way to Rajaratnam’s headquarters on the 16th floor, where they were escorted to his office, which was strategically placed within earshot of the trading floor. Almost as soon as Trehan spoke, it became clear that Rajaratnam was in one of his “gorilla moods.” The behavior may have been calculated to force his hand; if Trehan pulled out, Galleon alone could receive those lucrative management fees. The argument escalated, and Trehan eventually declared that he no longer wanted to be part of the partnership. He marched out of the office and sold his stake in the fund soon after.

Gupta stayed. Few knew it at the time, but he and Rajaratnam were already hatching a plan that would initiate his second act in the investment business. Months earlier, Gupta confided in Kumar that he intended to partner with Rajaratnam on building a new fund, Taj Capital, that seemed to marry his twin goals of polishing his legacy and getting rich in the process. Taj Capital, which was planned to be as large as $2 billion, was going to focus on investing in South Asia. As talks progressed, Gupta became a fixture at Galleon’s sleek new offices on the 34th floor of 590 Madison, one of the most prestigious corporate addresses in Manhattan. Rajaratnam eventually suggested that Taj temporarily decamp to offices adjacent to Galleon’s trading floor. Later, when Gupta was considering exercising an option to buy another 5 percent stake in the Voyager fund, Rajaratnam lent him $5 million. He told an old McKinsey colleague, Marshall Lux, that his new partner was “one of the most outstanding hedge-fund managers and a very close friend.”

During their unlikely partnership, Gupta and Rajaratnam never quite behaved as close personal friends. Their families never socialized on weekends; Gupta was not a guest on the Kenyan safari that Rajaratnam treated 70 of his closest friends and family to for his 50th birthday. Their friendship, in some sense, was as transparent as it was confounding. Rajaratnam offered Gupta the chance to get rich, while Gupta, by virtue of his relationships with world leaders and C.E.O.’s like A.G. Lafley of Procter & Gamble, offered him unparalleled access to high-quality private information. What was notable, however, was how significantly Gupta came to rely on Rajaratnam and how the balance of power in their relationship subsequently changed. Gupta, once freed from corporate life, began to loosen his guard. And in an apparent effort to ingratiate himself to his new friend, their relationship took a dark turn.

One month after Gupta’s ascension to Goldman Sachs’s board, in November 2006, Rajaratnam began to squeeze his new partner. Gupta had recently helped facilitate a loan from Rajaratnam to his friend Ramesh Vangal, whose company was trying to buy an Indian bank. As Vangal dragged his feet on repaying the loan, Rajaratnam’s gorilla mood re-emerged. This time it was directed at Gupta. On Dec. 21, Rajaratnam sent him an angry e-mail that seemed to hold Gupta responsible for the missing funds. “Under the circumstances,” he wrote, “I am not able to meet you for lunch today.” The note was perfectly timed to threaten the former McKinsey director. Taj Capital, his foray into the investment game, was in the midst of incorporation. Any hiccup could scuttle the deal. “And I am canceling all further meetings for Taj Capital,” the e-mail continued. It was signed formally, “Raj Rajaratnam.” The money he was owed arrived within a matter of weeks.

Gupta now seemed fully under Rajaratnam’s sway. On March 12, 2007, Gupta, sitting comfortably in the Galleon offices, dialed into an audit-committee meeting of the Goldman Sachs board. The meeting previewed Goldman’s first-quarter profits, which were set to be unveiled the next day. About 25 minutes after Gupta hung up, Galleon bought $91 million of Goldman stock — an odd trade for a fund that typically invested in companies like Intel and Google. When Goldman posted better-than-expected earnings, Galleon made $2 million on the trade. Over the next year, in June 2008 and then in September and October 2008, Gupta called Rajaratnam following Goldman board meetings. Soon after, the phone records indicate, Galleon funds made market-winning trades worth millions of dollars.