It was a balmy evening on April 23, 1935, when the cream of the motion picture industry gathered in Hollywood's ultra-trendy Victor Hugo Restaurant. The occasion was a white-tie affair at the invitation of writer Dorothy Parker to hear a man with whom many were familiar, some more intimately, literally, than others.

As the guest of honor rose to speak, "Jewels of incalculable value glittered in the radiant light of the chandeliers," writes Jonathan Miles in his new biography, "The Dangerous Otto Katz: The Many Lives of a Soviet Spy" (Bloomsbury, $26). Before him sat a dazzling who's who of Tinseltown: Fredric March, Norma Shearer, Jimmy Cagney, Samuel Goldwyn, Irving Berlin -- the list went on and on.

"You could have heard a sequin drop," as Rudolph Breda, a broad-shouldered, blue-eyed Czech, began to speak in impeccable English of his struggle against fascism and the Nazi menace. "Some were close enough to notice his barely detectable dueling scar. Here was a man of action, a fighter," Miles relates.

Breda spoke of hand-to-hand combat with German sentries as bullets "sprayed the air," of pulling off a death-defying leap into a river. The audience ate it up, so much so that Breda pocketed a hefty $40,000 that night for anti-fascist freedom-fighters.

Everything Breda said that night was a lie, Miles tells us. There were no brushes with death, no struggles with murderous storm troopers. The scar was not the result of a duel. Even his name was a lie. Breda was, in fact, Otto Katz, and he was no freedom fighter, but an agent of dictator Joseph Stalin's Comintern, the foreign arm of the Soviet Communist Party. The money he collected that night went straight to Moscow.

Katz, as this remarkable biography explains, was the quintessential showman, an actor of such skill that his audience that night in 1935 -- and on innumerable successive occasions -- paled in comparison. And he cut a wide swath through his admirers, especially the ladies. There is reason to believe, Miles writes, that Katz was married, albeit briefly, to Marlene Dietrich.

What Katz was not, the subtitle of the book notwithstanding, was a spy -- at least, not in the accepted sense of the term. He did not convey intelligence to Moscow. Rather, his role was that of a cultural operative, a salesman of the party line. Left-wing politics and "parlor pinks" were all the rage among the intelligentsia in 1930s Europe and America, and in this milieu Katz moved with the enthusiastic agility of a circus ringmaster.

It would end badly, of course. Katz was hanged in the early morning hours of Dec. 3, 1952, after days of torture at the hands of the Czech secret police and a confession to bogus charges of "pro-Zionist" activities. He had simply outlived his usefulness to Moscow, where the word came down to dispose of an embarrassment. Katz's name had popped up in sensational 1952 revelations that playwright and actor Noel Coward, with whom he had dealings, had been a British agent.

What a fascinating, expertly handled story this is. To say that it is exhaustively researched and felicitously written would be an understatement.

Through these pages moves a litany of the literary and artistic lions of the day, people whose passion for justice and the downtrodden was excelled only by a curious moral occlusion. Dupes, some called them. Lenin's term probably was more accurate: "Useful idiots."

Michael J. Bonafield is a night copy editor for the Star Tribune.