Prologue There is no way to know exactly when Charles William Thomas began to think about suicide. Who could really know such a thing? Years later, congressional investigators could offer only their strong suspicions about what had finally led Thomas, a former American diplomat who had spent most of his career in Africa and Latin America, to kill himself. On Monday, April 12, 1971, at about four p.m., he put a gun to his head on the second floor of his family's modest rented house, near the shores of the Potomac River, in Washington, DC. His wife, downstairs, thought at first that the boiler had exploded. Certainly two years earlier, in the summer of 1969, Thomas had reason to be disheartened. He was forty-seven years old, with a wife and two young daughters to support, and he knew his career at the State Department was over.

It was official, even though he still could not fathom why he was being forced out of a job that he loved and that he thought-that he knew -he did well. The department long had an "up or out" policy for members of the diplomatic corps, similar to the military. Either you were promoted up the ranks or your career was over. And since he had been denied a promotion to another embassy abroad or to a supervisor's desk in Washington, Thomas was "selected out," to use the department's Orwellian terminology for being fired. After eighteen fulfilling, mostly happy years wandering the globe on behalf of his country, he was told he had no job. At first, he thought it must be a mistake, his wife, Cynthia, said. His personnel records were exemplary, including a recent inspection report that described him as "one of the most valuable officers" in the State Department, whose promotion was "long overdue." After he was formally "selected out," however, there was no easy way to appeal the decision.

And Thomas, a proud, often stoical man, found it demoralizing even to try. He had already begun boxing up his belongings in his office and wondering if, at his age, it would be possible to begin a new career. He did have one piece of unfinished business with the department before he departed. And on July 25, 1969, he finished typing up a three-page memo, and a one-page cover letter, that he addressed to his ultimate boss at the department: William P. Rogers, President Nixon's secretary of state. Colleagues might have told Thomas it was presumptuous for a midlevel diplomat to write directly to the secretary, but Thomas had reason to believe that going to Rogers was his only real hope of getting someone's attention. Thomas was not trying to save his job; it was too late for that, he told his family. Instead, the memo was a final attempt to resolve what had been-apart from the puzzle of his dismissal-the biggest, most confounding mystery of his professional life.

Rogers was new to the State Department, sworn in only six months earlier along with the rest of Nixon's cabinet. Thomas hoped Rogers might be willing to second-guess the career diplomats at the department who-for nearly four years-had ignored the remarkable story that Thomas kept trying to tell them. At the top of every page of the memo, Thomas typed-and underlined-the word "CONFIDENTIAL." "Dear Mr. Secretary," he began. "In winding up my affairs at the Department of State, there is a pending matter which I believe merits your attention." The memo had a title: "Subject: Investigation of Lee Harvey Oswald in Mexico." His tone was formal and polite, which was certainly in character for Charles William Thomas, who used his middle name in official correspondence to avoid confusion with another Charles W.

Thomas who worked at the department. He wanted to be remembered as a diplomat-to be diplomatic-to the end. He knew his memo outlined potentially explosive national-security information, and he wanted to be careful not to be perceived as reckless. He had no interest in leaving the State Department with a reputation of being some sort of crazy conspiracy theorist. At the end of the 1960s, there were plenty of craven, headline-grabbing "truth-seekers" peddling conspiracies about President Kennedy's assassination. Thomas did not want to be lumped in with them in the history books-or in the classified personnel archives of the State Department, for that matter. His memo contained no language suggesting the personal demons that would lead him to take his life two years later. Secretary Rogers would have had easy access to the details of Thomas's career, and they were impressive.

Thomas was a self-made man, orphaned as a boy in Texas and raised in the home of an older sister in Fort Wayne, Indiana. He served as a navy fighter pilot in World War II, then enrolled at Northwestern University in Evanston, Illinois, where he earned both a bachelor's and a law degree. Foreign languages came easily; he was fluent in French and Spanish and, over the years, developed a working knowledge of German, Italian, Portuguese, and Creo≤ the last had been valuable during a diplomatic posting in Haiti. After Northwestern, he studied in Europe and received a doctorate in international law at the University of Paris. In 1951, he joined the State Department and served initially in hardship posts in West Africa, where, despite several severe bouts of malaria, he was remembered for his good humor and enthusiasm. His friends said he was "the diplomat from central casting"-six feet tall, blond, preppy handsome, articulate, and charming. Early in his career, colleagues assumed he was destined to achieve the rank of ambassador, running his own embassy. In 1964, Thomas was named a political officer in the United States embassy in Mexico, where he was posted for nearly three years.

Mexico City was considered an especially important assignment in the 1960s since the city was a Cold War hot spot-Latin America's answer to Berlin or Vienna. There were big Cuban and Soviet embassies, the largest in Latin America for both Communist governments. And the activities of Cuban and Soviet diplomats, and the many spies posing as diplomats, could be closely monitored by the United States with the assistance of Mexico's normally cooperative police agencies. The CIA believed that the Russian embassy in Mexico was the KGB's base for "wet operations"-assassinations, in the CIA's jargon-in the Western Hemisphere. (It would have been too risky for the KGB to run those operations out of the Russian embassy in Washington.) Mexico City had itself been the scene of Kremlin-ordered violence in the past. In 1940, Soviet leader Joseph Stalin dispatched assassins to Mexico City to kill his rival Leon Trotsky, who was living there in exile. Mexico City's reputation as a center of Cold War intrigue was cemented by the disclosure that Lee Harvey Oswald had visited the city only several weeks before the assassination of President John F.

Kennedy in Dallas on Friday, November 22, 1963. Details about Oswald's Mexico trip were revealed in news reports published within days of the president's murder, giving birth to some of the first serious conspiracy theories about foreign involvement in the assassination. Everything about Oswald's stay in Mexico, which had reportedly lasted six days, was suspicious. A self-proclaimed Marxist, Oswald, who did not hide his Communist leanings even while serving in the U.S. Marine Corps, visited both the Cuban and Soviet embassies in Mexico City. It appeared he had gone there to get visas that would allow him, ultimately, to defect to Cuba. It would be his second defection attempt.

He had tried to renounce his American citizenship when he traveled to the Soviet Union in 1959, only to decide to return to the United States from Russia three years later, saying that he had come to disdain Moscow's brand of Communism, with its petty corruptions and mazelike bureaucracy. He hoped Fidel Castro and his followers in Havana would prove more loyal to the ideals of Marx. In September 1964, the presidential commission led by Chief Justice Earl Warren that investigated Kennedy's assassination, known to the public from the start as the Warren Commission, identified Oswald as the assassin and concluded that he had acted alone. In a final report at the end of a ten-month investigation, the seven-member panel said that it had uncovered no evidence of a conspiracy, foreign or domestic. "The commission has found no evidence that anyone assisted Oswald in planning or carrying out the assassination," the report declared. While the commission could not establish Oswald's motives for the assassination with certainty, the report suggested that he was emotionally disturbed and might have decided to kill the president because of "deep-rooted resentment of all authority" and an "urge to try to find a place in history." And in the final days of his employment at the State Department in the summer of 1969, those were the conclusions that Charles Thomas wanted someone in the government to revisit. Was it possible that the Warren Commission had it wrong? Thomas's memo to Secretary of State Rogers outlined information about Oswald's 1963 Mexico visit that "threatened to reopen the debate about the true nature of the Kennedy assassination and damage the credibility of the Warren Report.

Since I was the embassy officer who acquired this intelligence information, I feel a responsibility for seeing it through to its final evaluation," he explained. "Under the circumstances, it is unlikely that a.