THE CIA'S CLOSET is large and cluttered, the air inside dank and dismal, obscuring the skeletons of abuses past. Until recently, the entrance had been tightly bolted. But here comes Thomas Powers, flashlight in hand, following in the footsteps of others making a more complete tour, illuminating more hidden recesses and rattling more skeletons than anyone else.

His unwitting tourguide is Richard Helms, who rose quietly but steadily for nearly 30 years through the Agency's ranks, responsible for many of its most sensitive--and later embarrassing--covert operations. As chief of the clandestine operations division in the '50s, as a Deputy Director in the early '60s, and finally, from 1966 to 1973, as head of the CIA, Helms' efforts spanned the globe--from Chile to Cuba to the Congo to Southeast Asia to Italy and Eastern Europe, and always, always, to the USSR: anticommunism is the lifeblood of the CIA. In 1977 Helms explained what had worried him most as CIA director--not fighting secret wars, not overturning free elections, not the press, not Watergate, but..."The CIA is the only intelligence service in the Western world which has never been penetrated by the KGB. That's what I worried about."

Ironically, it was not KGB infiltration that led to his downfall, it was domestic politics. By foregoing the flamboyance of some of his colleagues, Helms had also lacked their visibility--and thus did not make an easy target or scapegoat when CIA projects went awry, as they did with increasing frequency after the early "successes" of the Cold War. He covered his tracks well, and when superiors sacked other, more imaginiative CIA men in the shake-ups that followed such failures as the ill-advised backing of Indonesian rebels against Sukarano in 1958 or the doomed Bay of Pigs invasion in 1961, Helms was passed over; he was a survivor.

Until Watergate. Helms is bitter now. He comes across as too much a true believer in CIA ethics to write his memoirs and spill the many secrets that no doubt still remain hidden in that spacious closet. But he wants the record set straight--or at least set it his way--on the CIA's involvement in Watergate. Helms says Nixon fired him in 1973 and banished him to Iran (as ambassador) because the President was furious when Helms refused to enlist the CIA in the Watergate cover-up. The CIA was not directly behind the break-in (though some who were had worked for the Agency), says Helms, and the facts seem to back him up.

Helms' resentment increased when members of the Nixon White House, such as Chuck Colson and H.R. Haldeman, began hinting that Watergate may have been, after all, a CIA operation; and it peaked when John Ehrlichman wrote The Company, which featured a CIA director very much like Richard Helms black-mailing a President very much like Richard Nixon: give me an ambassadorship or I'll expose Watergate's sleazy underside. Why the hell would I want to be ambassador to Iran? says Helms.

I never blackmailed Nixon in any form, manner or kind...I work for the President of the United States. I would have been disloyal, treasonable or anything you want to call it, if I'd tried any such trick and I certainly did not...I'm being a little bit positive in raising my voice...because I want to convey to you the fact that I mean it.

The passage is one of the few in The Man Who Kept the Secrets where Helms becomes emotional, where he seems anything more than the competent paper pusher who keeps things moving without rocking the boat. Although it is commonly recognized that the CIA acts on the whims and wishes of whomever occupies the White House, and not as the non-partisan intelligence-gathering organization originally envisioned in the National Security Act of 1947, the crassness of Nixon's attempt to use the CIA for domestic politics apparently struck a raw nerve in Helms.

And Helms became even more disturbed when revelations of past covert activities began trickling out a Watergate unfurled, finally exploding onto the front page of The New York Times in December 1974, and then in the hearings of the Senate Select Committee on Intelligence. Powers details how the CIA, on orders of five presidents, had sabotaged elections, overthrown governments, destroyed men and movements, and routinely interfered in the internal affairs of other countries--spending unknown fortunes in the process. And presiding over the treasonous disclosures was Helms' successor (after James Schlesinger '50's short reign) William Colby, reluctant, but cooperative as the secret history became--to an extent--public knowledge.

As it did, the primary rationalization behind the CIA's illegal activities--"the Russians do it too, and worse, so we have to respond"--all but disintegrated. Agency men resorted to another: "We were just following orders." Though Helms and others declined to implicate the chief executives in the most sensitive operations--for example. John F. Kennedy '40 in the attempts out Fidel Castro's life--the message was clear: the CIA was not, in Frank Church's phrase, "a rogue elephant rampaging out of control." The orders had to come from somewhere.

In the post-Watergate climate, politicians no longer bought this Eichmannesque reasoning, and went after Helms in characteristically timid fashion. Typically, writes Powers, "Helms was not charged with what he did, but more narrowly for having lied about it." Asked by the Senate Foreign Relations Committee in 1973 whether the CIA had tried to overthrow the government of Chile or passed money to Salvador Allende's opponents, Helms replied, simply, "No sir." Perjury.

Some accounts say Helms threatened to spill every dark secret he could dredge up if he were brought to trial; Powers ignores this scenario. In any case, in 1977 Helms' lawyers reached a deal with Attorney General Griffin Bell that allowed him (in exchange for a plea of nolo contendre) to escape with a suspended two-year jail term, a $2,000 fine paid by sympathetic colleagues, and his federal pension intact.

Helms remains unrepentant: "I'll wear this conviction like a badge of honor...I don't feel disgraced at all." His world view crystallized long ago into patterns of Cold War confrontation. But one cannot gauge Helms the individual from The Man Who Kept the Secrets. Touching only briefly on Helms' personal life, Powers attempts to tell the secret history of the CIA by using his career as a reference point; since Powers portrays Helms only in his Langley office persona, he appears for the most part as just a particularly durable background actor in a play where the cast changes with every act. Aside from a stubborn devotion to career and crustified politics. Helms' colorlessness is his most distinguishing characteristic. He believes he has done his duty and served his country.

Powers seems to like Helms personally and while he rejected as anachronistic the CIA mentality--"Helms belongs to the past"--he does not beg the question. Quite correctly, Powers tries to avoid a prosecutorial approach. To assess the CIA's performance in it first 30 years, one needs not a D.A. but a diligent historian.

Inevitably, there are gaps and errors in The Man Who Kept the Secrets; too many people have died, too many documents have been destroyed, too many decisions never made it to paper--and too many persons still have reason to prevent the whole truth from surfacing. But Powers has compiled an impressively documented and reasonably well-presented litany of power and its abuses; his book--a most thorough work but by no means the last word on the subject, will provoke, frighten and outrage even those already jaded by the sleaziness and corruption of Watergate. Richard Helms and the old boys at the CIA would have been much happier it Thomas Powers and others like him never bothered to look inside their murky closed. It may not be pleasant, but it is important and necessary to inspect those skeletons and pick the bones clean; we can learn from the post-mortems how better to fight the disease.