IN HIS THIRTY-FIVE years of life, Paul Nizan was a key intellectual in the French Communist Party. He published three novels, polemical essays, translations and a large quantity of militant journalism on home and foreign affairs. He left the Party on the signing of the Hitler-Stalin pact in 1939. In his excellent study, Michael Scriven offers no facile answer to the conundrum: how could Nizan be a Stalinist journeyman one minute, and a subtle novelist in the finest French tradition the next? Undeniably, Nizan succeeded in this passably schizophrenic feat. In his melodramatic review of The Conspiracy, printed as an afterword to Quintin Hoare's scrupulously accurate translation, Sartre, who once said that, apart from a few women, Nizan was the only true friend he ever had, and his intellectual pathfinder and superior, asks the loaded question: 'Can a communist write a novel? He does not have the right to make himself an accomplice of his characters' (ie his bourgeois characters). His ideological strabismus disqualified him from seeing that Nizan in this novel marries an implacable critique of his youthful heroes with a complicitous understanding of their follies.

Students at the Ecole Normale Superieure in the late Twenties go in for sex-games, play-acting, mental toying with a largely metaphysical politics, but not inane horse-play a l'Oxbridge. Even in their frequent daftness they are serious. The conspiracy of the title is multiple: that of families against adolescents and vice versa; that of leftish students against the rotting but apparently indestructible capitalist system; that of the police against the Communist Party, driven into secrecy by swoops against its leading figures; and that of all those forces which conspire against wilful imposition of change. In this framework of interlocking but mutually hostile sub-worlds, betrayal dominates. Rosenthal, the charismatic force of the group, does nothing with the documents of military and industrial espionage he urged other members to procure, with the aim of aiding the Soviet Union's attempt to catch up technologically with the West. His inverted counterpart Pluvinage, the only one of the group to plunge into membership of the CP, betrays it by informing on a party leader in hiding and then this born loser commits moral suicide in deserting the party for the secret police.

Nizan moves with assurance between the political and the sentimental educations of his young men. Rosenthal's liaison with his sister-in-law, initiated as a slap in the chops of bourgeois convention, seduces him away from the world of heavily intellectualized activism. When the scandal is effortlessly absorbed by the family tribunal