It's a thread that runs from horrified young intelligence operatives stumbling into the death camps of Nazi Germany to hardened agents running assassination programs in the jungles of Vietnam to august men of state building a shadow government with secret decrees authorizing tyranny, murder, torture and deceit. It's a thread of moral corruption, corruption by an idea, a temptation, a perversion of reason, the whisper of evil that says: "The end justifies the means."

That thread fetched up briefly again last week, then was buried, literally, in a Maryland grave. The family of Frank Olson laid his exhumed remains to rest, closing the book on their half-century of struggle to find out why he died so violently at the hands of the government he had served -- and whose deepest secrets he had guarded.

Frank's son, Eric, believes he knows the answer now: His father was murdered to keep the thread from sight, to "protect" the American people from the knowledge that their own government had taken up and extended Nazi experiments on mind control, psychological torture and chemical warfare -- and that it was conducting these experiments as the Nazis did, on unwilling subjects, on captives and "expendables," even to the point of "termination."

Frank Olson was a CIA scientist at Fort Detrick, Maryland, the U.S. Army's biological weapons research center. Ostensibly he was a civilian employee of the Army; his family didn't know his true employer. Olson worked on methods of spreading anthrax and other toxins; some of his colleagues were involved in mind control drugs and torture techniques.

In November 1953, one of these colleagues slipped him a drink laced with LSD -- part of a secret "field experiment" with the new hallucinogen. A few days later, a supposedly mentally unhinged Olson leapt to his death from a hotel room in New York City. The government told the family it was simply a tragic suicide. They didn't mention the LSD -- or the fact that Olson worked for the Central Intelligence Agency.

In 1975, during congressional hearings into CIA abuses, Eric Olson learned for the first time about the CIA's involvement in his father's death. After threatening to sue, the family was hastily given an audience with President Gerald Ford, who personally apologized for the agency's indirect involvement -- that LSD test gone awry -- and arranged a $750,000 settlement to keep the case out of court. The director of the CIA, William Colby, also met the family and gave them what he claimed was the CIA's complete file on the unfortunate case.

But it was all a lie. Once again they concealed the CIA connection. They didn't tell the family that Olson had been considered a security risk or mention what he'd discovered about his colleagues' research. All this was left to Eric Olson to piece together over the years -- in obscure archives, through lucky accidents and strained meetings with old CIA hands, revealing dribs and drabs of the truth -- a quest documented by Michael Ignatieff in The New York Times.

In the summer of 1953, a few months before his death, Frank Olson made several trips to Europe to investigate secret U.S.-British research centers in Germany. There he found the CIA was testing truth serums and other torture drugs on expendables, including captured Russian agents. He told a British colleague that he had witnessed "horrors" there. And it called into starkest question his own work on biochemical weapons. He came home a changed man, troubled, morose. He told his wife he wanted to leave government service.

But it was too late: The brutal machinery was already grinding. His British colleague told his own superiors about Olson's concerns; they in turn informed the CIA that Olson was now a "security risk." Not long after his return, Olson was given the LSD. Then he was flown to New York, ostensibly for psychiatric treatment, at the hands of a CIA doctor -- who prescribed whiskey and pills. Then he was taken to a CIA magician -- yes, a magician -- who apparently tried to hypnotize him for interrogation.