On Sunday, Aug. 20, 1911, the Mona Lisa was hanging in her usual place in the Louvre, in the Salon Carré between Titian's "Allegory of Alfonso d'Avalos" and Correggio's "Mystical Marriage." It was hot in Paris. "For more than 50 days," R. A. Scotti writes in "Vanished Smile," "temperatures had rarely dropped below 90 degrees. The country beyond Paris was burning. Thatch-roofed farmhouses and acres of parched forest had become tinder, and spontaneous-combustion fires broke out near Poitiers, Orléans and Beaumont, Albertville, Dijon and Fontainebleau." Inside the Louvre it was sweltering, and an overweight guard named Maximilien Paupardin, who worked in the Salon Carré, had eaten too much cassoulet at lunch. He was lethargic, drooping. When he left that evening, Leonardo da Vinci's masterpiece was hanging on the wall. When he returned two days later the Louvre was closed on Mondays all that remained, Ms. Scotti writes, "were four iron hooks and a rectangular shape several shades deeper than the surrounding area." The world's most famous painting had been stolen. Now there's a lovely set-up for a crime caper, and in this case, it's true crime. Ms. Scotti's svelte book tells the story of that long, hot August in Paris, when the world discovered that the Mona Lisa had disappeared. The painting was missing for more than two years, and the names of the prime suspects in the case Pablo Picasso and his friend, the poet and art critic Guillaume Apollinaire push this story past something even Dan Brown could concoct. Yes, this tale has been related before. But Ms. Scotti's book shows that this recondite shaggy-dog story is well worth revisiting. When word got out about the Mona Lisa's disappearance, France went into mourning. Thousands lined up to see the blank square on the wall; people left flowers and notes. It was like Diana's death without "Candle in the Wind." Mourning became rage. The Louvre, it turned out, had pathetically lax security. Most paintings weren't secured to walls. Photography was new at the time, and photographers were allowed to borrow works to shoot whenever they felt like it. The Mona Lisa had been placed in a glass box, but, as the thief proved, it could be easily removed. The director of the Louvre was traveling in Mexico when the Mona Lisa was stolen. When he returned, he was sacked. He should have known, most felt, that the painting would be a target. As Ms. Scotti writes: "Mona Lisa often made men do strange things. There were more than one million artworks in the Louvre collection; she alone received her own mail." A year before the Mona Lisa was taken, a man shot himself in front of her. Some worried that the stolen painting might be put to icky use. Ms. Scotti writes: "A Sorbonne psychology professor warned in Le Temps that the thief might be a sexual psychopath who would treat Mona Lisa with a 'sadistic violence and fetishistic tendresse,' take pleasure in 'mutilating, stabbing and defiling' her, then return her when he was 'through with her.' " Who did steal the Mona Lisa? Leonardo painted her not on canvas but on a solid panel of white poplar. You could not just roll the thing up and stuff it down your pants leg. After other leads fizzled, attention turned to Picasso and Apollinaire and their gang of young, avant-garde poets and artists. This group, sometimes called la bande de Picasso, was famous for its seething dislike of the kind of stale museum art that the Louvre represented. Apollinaire had signed a manifesto that threatened to "burn down the Louvre." It turned out that Apollinaire had sheltered a young man who had stolen several items from the Louvre; two of those items, small sculptures, were found in Picasso's apartment. Both men landed in the news media's glare, and Apollinaire was briefly arrested. It was a life-changing experience for him. To prove his patriotism, which had been questioned during the Mona Lisa affair, he enlisted in the French army in World War I. He was injured in the head by shrapnel in 1916 and died two years later at 38. When the actual thief was caught, his identity turned out to be, to those who thought a swashbuckling international criminal might be involved, a letdown. He was an Italian named Vincenzo Peruggia, who had worked at the Louvre. He was a patriot who simply wanted to return the Mona Lisa to his home country. (It had been acquired by France's King Francis I.) He was arrested while trying to sell the painting in Florence. Mr. Peruggia actually did get the Mona Lisa displayed in Italy, if only briefly. For a few emotional days after the painting was recovered and before it was returned to France, the Mona Lisa was shown in the Uffizi Gallery in Florence and then taken on a brief tour of Italy. This story does not end there, however. Many people refused to believe that Mr. Peruggia could have been a lone actor, and there are several conspiracy theories that Ms. Scotti works to track down, leaving the story intriguingly hanging. Why so much plot summary in this book review? Well, it's a good story to unpack. I've also been delaying the news that "Vanished Smile," for all its piquant details and plot-driven gleam, is a rusty, rattling, unsafe-at-some-speeds contraption. Ms. Scotti's prose is shrewd one moment, inept the next. When I read this line "Night like liquid velvet settled over the mansard roofs, innocent, if a night is ever innocent" I hoped for a moment she was kidding. Nope. Ms. Scotti ladles on some painful Dan Ratherisms. One character wears a "fedora with a brim the width of Texas" and is "as subtle as a banner headline." Picasso and his gang ride "into town like the cowboys of the Wild West." The author explains that the derogatory slang term "macaroni" was sometimes used, at the time, to refer to lower-class Italians in France. If she had used it once or twice, that would be one thing. When she deploys it five times in little more than 200 pages, it begins to be unpleasant. But enough. Rusty "Vanished Smile" may be, but it gets the job done. It's a rolling, clattering piece of entertainment. Ms. Scotti reminds us of the bedrock appeal of the Mona Lisa's gaze: "Each person who looks at her becomes the only person in her world."