IN The Menu Cypher talking turkey is raised to ingenious comic heights. The CIA agents posing as academics at Columbia University banter in a secret code with a food motif and lock horns with inspired craziness. But, suddenly, author Richard Elman switches tone and the scholarly spies put away their toys as a political conscience cuts through the frivolity. For the reader this jarring comic derailment -- to use the hero's description of a moment of intense displeasure -- is "like the face of Lillian Hellman in one of Mary McCarthy's nightmares."

In this sequel to Elman's favorably received The Breadfruit Lotteries, the spies of academia have their own familial lingo, a kind of nonsense dialogue without verbs; they ring out variations on the set "menu cypher," talking in a series of disjointed words that even those Americans steeped in pork-out pop culture would initially find difficult to comprehend. It is difficult to give examples of this verbal insanity since stray quotes would make little sense out of context. But if one isn't impatient, the reader soon catches on to the odd word play, the free associations, the constant metaphors and the heady, poetic beat.

Elman has wisely included a "Menu Cypher Glossary" of about 150 terms and their secret meanings. These covert definitions run the gamut from the bureaucratically clever ("Dutch Oven: Local security forces; mum's the word"), to the agreeably silly ("Yam: Spanish; also lingo for 'I am' "), to the cruelly funny ("Fast Food: The rush you feel when killing; also called a quicky"). After the reader adjusts to the burlesque of the language, one is in for a treat, especially when Mardyke -- a kind of mad, sodden version of comic Robin Williams -- takes over the floor with his succinct put-downs, berating an uncomprehending operative with "Use your egg cup" or railing at a TV screen showing a crying mother with "Medea's the message." Mardyke is hero Robert Harmon's browbeating boss, and even Harmon has a difficult time keeping up with Mardyke whose "metaphors were as remote to me as calling our Arabist colleague, Said Said, the pits because he sometimes ate olives." Harmon, a professor of "the history of ideas" at Columbia, is considering retiring from the CIA, perhaps a bit disillusioned about certain distasteful covert activities but mostly concerned with the recent gruesome deaths of other academics like Professor Smackover who was pushed through a paper-shredder or another hapless spy who was skewered on the cooling rods at the still-uncompleted Shoreham, Long Island, nuclear plant. Even his old pal Mohammed Dangerfield has bit the dust. Dealing with Mardyke's bombast and his colleagues' barbs ("you must think of us as a university without students, not a school for spies") sends him into the nonchalant arms of his psychiatrist who answers Harmon's complaints with, "It's your life. Do as you please . . . you'll die of cancer soon enough." To his midlife and romantic crises the doctor observes, "Mother, mother everywhere, and not a drop to drink."

His self-esteem somewhat intact, Harmon dodges an assassin's bullets for a while but is gunned down later by a femme fatale whose smile "like a fresh-tossed salad" soon has him doubled over and falling right into his cocky-leaky soup. After hospitalization, Harmon leaves confidently for a mission in Latin America meticulously disguised as a Salvadoran physician. But his confidence evaporates when he deplanes and a transvestite ("Color me quencher") looks him over and says, "If your name is Tinora, Doctor, my name is Evita Per,on played by Patti Lupone and the name of dis place is Shrimp Creole."

The novel up to this midway point is a ripsnorter and its rhythmic, satirical jabs at U.S. foreign policy are subtly biting as well as poetically precise. But then these dialogue-drenched vignettes crash into the rhetorical, virtually actionless second half with an incongruous thud. The turkey-talking agents end up eating crow.

The somewhat leftist Harmon is kidnapped by the Nicaraguan military; and we are given a short orientation on their repressive intentions. Later, as the pages get grimmer and grimmer, Harmon runs into his friend Randall Pullman (who figured highly in The Breadfruit Lotteries) who, in a long digression, describes the horrors in El Salvador: "Villagers strafed when they try to find refuge . . . fields scorched . . . corpses along the highway. Gang rapings . . . This is not vulgar Marxism I'm spouting, Robert." Even the second glossary that Elman provides ("An Ethiopian's tears, a white man's ballet: Blood is thicker than water") is solemn and heavy-handed. And when an agency official jokes about the Maryknoll nuns, Elman has really gone too far.

That the cynically violent denouement is curiously flat and unaffecting comes as no surprise considering the novel has to coast on the good will built up in its ribald first half. Had the comic tone been sustained with Harmon turning the agency's supposed foolishness on its ear, this could have been a crackerjack satire. But Harmon settles his mid-life crisis by simply retiring. What begins as a prodigiously funny flight-of-fancy dive-bombs and crashes right on the coast of Missed Opportunity.