Assuming that these documents are authentic, they pose several intriguing questions with which Mr. Hougan does not grapple. Under the Brady rule, prosecutors must turn over any exculpatory evidence - that is, evidence which would tend to show a defendant's innocence - to defense attorneys. Since the Watergate burglars were charged, among other things, with violations of the Federal wiretapping laws, these memorandums would certainly appear to be exculpatory. Did Mr. Silbert turn this evidence over to the defense? If so, why did it never surface? Most curious of all, since the F.B.I. at this time was run by the most malleable of Nixon appointees, L. Patrick Gray, why didn't Mr. Gray go public with the lab's reports, which would certainly have aided the embattled White House and even turned the scandal back on the Democrats?

Nonetheless, these memorandums are important. For we know from several sources that Mr. Baldwin, in his room at the Howard Johnson Motor Inn, was listening to intercepted conversations early in June. If not Oliver's phone, then whose phone was he listening to?

It is here that ''Secret Agenda'' becomes more speculative. The author believes that Mr. Baldwin was listening in on several call girls at the Columbia Plaza Apartments. He does not identify them. But he calls the key one ''Tess'' and suggests that she was connected to a Washington lawyer named Phillip Bailley, who was charged in June 1972 with running a Washington call girl ring.

According to Mr. Hougan, Phillip Bailley's arrest spread ''alarm'' through official Washington because a pair of address books seized from his apartment - and a client list found in a raid on the Columbia Plaza - contained the names of prominent Republicans and Democrats. Mr. Hougan also reports that Phillip Bailley was amorously connected with ''a White House attorney with a penchant for being horsewhipped and an executive secretary on Capitol Hill who was not only beautiful and politically active but more than a little inclined toward voyeurism, sadomasochism and zoophilia.''

This is not the first time that such steamy stuff has surfaced in connection with Watergate. According to John Ehrlichman, the alleged tap on Mr. Oliver's phone recorded him ''phoning his girl friends all over the country lining up assignations.'' I and others reported unconfirmed rumors that the telephone was being used for some sort of call girl service catering to prominent Washingtonians.

But Mr. Hougan has pushed this farther. He suggests that the tap of Tess's phone was indeed intercepting conversations on Mr. Oliver's phone because a D.N.C. secretary was using that phone to introduce visiting Democrats to Tess. Mr. Hougan does not identify the secretary at this point, but later strongly suggests that it was Ida ''Maxie'' Wells, Mr. Oliver's personal secretary, a name that will figure again in his scenario. The tap on Tess's phone, Mr. Hougan says, was placed by Louis Russell (since deceased), a ''drunken, whoring and brutish'' figure who had once been a staff member of the House Committee on Un-American Activities and was now working for James McCord's private security firm.

Like many others who have studied Watergate, Mr. Hougan is skeptical about Mr. McCord's (and E. Howard Hunt's) ''retirement'' from the C.I.A. Therefore, he concludes that Russell too was working for the Agency. Ergo, the taps on the prostitutes' phones - and probably the call girl operation itself - were a C.I.A. project, designed to gather information about the sexual activities of prominent Washingtonians, perhaps for blackmail, perhaps to construct psychological profiles.