Mr. Bowen, who is now 66 and teaches accounting at the University of Texas, Dallas, was fired in January 2009. (After signing a separation and confidentiality agreement, he received a severance package of less than $1 million.) And Citigroup went on to receive a $45 billion bailout from the taxpayers, plus guarantees on nearly $300 billion of securities, some of which were most likely crammed with the very low-quality mortgages Mr. Bowen had warned about.

America became inured to the sight of one extremely wealthy former Goldman Sachs senior partner turned Treasury secretary (Mr. Rubin) asking another (Mr. Paulson) for a favor. But what Mr. Bowen believes happened to him after Citigroup fired him still has the power to shock anyone who cares about accountability and justice. He feels he was muzzled; others involved are adamant that he was not.

In 2008, after his note to Mr. Rubin and after his responsibilities were vastly reduced at Citigroup, but before he was fired, Mr. Bowen decided to become a whistle-blower. That April, he filed a complaint, under the Sarbanes-Oxley Act of 2002, with the Occupational Safety and Health Administration claiming he had been retaliated against after writing his e-mail to Mr. Rubin. (The complaint was settled as part of his separation agreement with Citigroup.) Then, in July, Mr. Bowen went to the Securities and Exchange Commission. “I testified before the S.E.C.,” he told an audience in Texas earlier this year. “I told them what had happened.” He gave the S.E.C. more than 1,000 pages of documents. “Mr. Bowen, we are going to pursue this,” the agency told him. He never heard back. “Not only did they bury my testimony, they locked it up,” he said in his speech. (The S.E.C. has denied my numerous requests under the Freedom of Information Act for access to Mr. Bowen’s file, even though he has given his permission, claiming that the material was “confidential” and included Citigroup “trade secrets.” On Sept. 11, the S.E.C. denied my administrative appeal of its decision.)

In May 2009, Congress created the 10-member Financial Crisis Inquiry Commission, or F.C.I.C., to examine the causes of the financial crisis. Led by Phil Angelides, a former state treasurer of California, it was empowered to get to the bottom of what had happened and why. The F.C.I.C. invited Mr. Bowen to an interview after an investigator read his Sarbanes-Oxley complaint.

Mr. Bowen was excited to finally be able to share his story. What’s more, he told me, he could tell all, freed from various provisions of his confidentiality agreement with Citigroup.