France is agog over a new murder mystery -- a tale of intrigue in high society that features the prime minister's best friend as the victim and the nation's most celebrated woman jockey as the ambitious and estranged wife of the dead man.

The saga has come as a godsend to newspaper editors already bored with the somewhat sluggish campaign for nationwide elections in March. Every day seems to produce an intriguing new detail about the beautiful people caught up in a plot worthy of an Inspector Maigret novel.

"It's incredible, the things one learns," remarked President Francois Mitterrand at a recent reception, acknowledging to reporters that he, too, was fascinated by the case of Jacques Perrot, a brilliant 39-year-old lawyer.

The story begins with the discovery of Perrot's corpse on the doorsteps of a plush Paris apartment belonging to his parents, just two days before the New Year. Evidence gathered at the scene suggested that the murder had been carried out by professionals tipped off about the lawyer's whereabouts.

Intense public interest in the murder was guaranteed by Perrot's jet-set status and his friendship with Prime Minister Laurent Fabius. Childhood buddies, the two men shared a passion for horseback riding. They liked to have lunch together every week and were best men at each other's weddings.

Also intriguing was the personality of his 27-year-old widow, Darie: the holder of university diplomas in Russian and art history, the first woman ever to win the French horse race known as the tierce, the star of a popular radio talk show. Beautiful, intelligent and ambitious, she shone on the Paris social circuit.

As French newspapers vied with each other to reconstruct the last few weeks of Perrot's life, it quickly became apparent that the image of high-society bliss projected by the color magazines was a sham. Their marriage, in fact, was on the rocks. According to his friends, Jacques was separated from Darie and planning divorce proceedings.

Shortly before his death, according to these accounts, Perrot made some startling discoveries about his wife's family, the Boutbouls. He learned that Darie's father, a dentist officially declared dead in an air crash, was alive and well and living in the center of Paris. He also discovered that her mother, a wealthy racehorse owner, had been disbarred as a lawyer by a legal disciplinary commission after being accused by a religious charity of swindling the equivalent of $2 million.

With hordes of paparazzi camped outside Darie's Paris apartment, the Boutbouls decided to give their version of the story. They chose as their confidant the horse-racing correspondent of the state television channel, Antenne 2, Pierrette Bres. Bres was reported to have told Darie that she owed an explanation to the millions of racing enthusiasts who bet on the tierce week by week.

Courtesy of Antenne 2, which arranged a meeting between Darie and her father, television viewers were treated to an emotional reunion of the Boutboul family. As the cameras zoomed in for a close-up, Darie collapsed sobbing into the arms of a man she had supposedly not seen since she was a small girl. Rival news organizations questioned the authenticity of the reunion.

WhyRobert Boutboul pretended that he was dead for 16 years is still a mystery. The family's explanation is that his disappearance was an alternative to the ordeal of going through a divorce. A benign-looking 73-year-old, he told Bres that his wife thought it would be better for everybody concerned if he simply vanished.

The French police now are trying to establish if there was a link between Perrot's death and the unraveling secrets of the Boutboul clan. One theory advanced by the slain man's friends is that he had been seeking to bargain his own silence for custody of his 4-year-old son, Adrien. Darie, however, has denied that custody of the child was a major dispute.

Following the principle in French murder mysteries of cherchez la femme (look for the woman), the French press seems to have picked on the Boutboul family as the key to the solving the case. Last week, Perrot's mother-in-law, Elisabeth Boutboul, was questioned for 20 hours straight. But both she and her daughter have alibis for the time of the slaying. Interviewed by Antenne 2, Mrs. Boutboul said she thought her son-in-law's killing was connected to his "curiosity."

"When you touch dynamite, you can get burned," she added, hinting darkly that she knew more about the background to the murder than she was prepared to reveal.

Under headlines like "The Boutboul Dynasty -- France's Answer to Dallas," the French press has tried to satisfy its readers' thirst for tidbits about life in the fast lane. Le Nouvel Observateur, a somewhat staid magazine for left-wing intellectuals, carried a vivid description last week of the fits of rage thrown by Darie when her husband insisted that they go to dinner with the prime minister.

"I can assure you it is very difficult to be friendly with Francoise Fabius," Darie, who actively supported the right-wing neo-Gaullist party, was quoted as saying of the prime minister's wife in an interview.

As for Fabius, he has preserved a dignified silence about the Boutbouls. Eulogizing Perrot on television as his "closest friend," he added emotionally: "He was a man of incredible generosity and kindness. I wish that amid all this noise, people would first of all think of him and of the sorrow of those who loved him."