FLORENCE, Italy Maurizio Seracini claims not to be pleased that he is the only person mentioned by his real name in "The Da Vinci Code." A scientist turned art detective, he has no need for any manufactured mystery around Leonardo. For 32 years he has chased a real one and he seems now, finally, poised to solve it. It is a long, and satisfyingly complex, story. But it can be summed up with one question: What happened to "The Battle of Anghiari," a grimacing crunch of men and horses considered by some experts to be Leonardo's greatest painting? Mr. Seracini thinks he knows, and he was recently given permission to restart his search, which involves using the most modern detecting equipment to peer through a 500-year-old wall in the Palazzo Vecchio here. On that wall, in 2002, he found a tantalizing crevice behind a Vasari fresco where the Leonardo may be. If he succeeds, he could bring to light what one Leonardo scholar calls potentially "one of the great art finds of all time." Or he could find nothing. Or he could find the painting wrecked by time and its own defects. In any case, after three obsessive decades Mr. Seracini is very much on the hook. "I have to say, there is enough here to make you scratch your head scratch it to the point of losing your hair," Mr. Seracini, a dapper 60 with, so far anyway, a full head of white hair, said as he stood in the room where he believes the painting is hidden. "It's very intimidating." One of the few certainties is that the painting, or at least a part of it depicting a fight for a standard, did exist on the wall of the Palazzo Vecchio, the old home of the Medicis. "Friday the 6th of June, 1505, at the stroke of the 13th hour," Leonardo wrote in one of his notebooks, "I started to paint in the palace." His younger rival, Michelangelo, had also been commissioned to paint his own battle scene on the opposing wall. Michelangelo left for Rome and never began painting it. But both men produced preparatory cartoons considered not only among the finest ever created but exemplary of the two strains of Renaissance the men embodied: Michelangelo drew heroic bathing nudes; Leonardo worked the motion and fury of men and horses in action. Vasari called Leonardo's cartoon "most excellent and masterful for its marvelous treatment of figures in flight." But Leonardo started much and finished little. Technical problems he painted not on wet plaster like traditional fresco, but with oils on a wax-impregnated wall haunted him. Only a small portion was completed, though it was Leonardo's largest painting, perhaps 15 feet by 20 feet, and as extraordinary as the cartoon. Several copies were made, one by Rubens. Even in 1549, a letter writer urged a friend to have a look, calling it a "marvelous thing." Beginning in the 1560s, Vasari, who also built what is now the Uffizi museum, began to restructure the room. He enlarged it and covered both walls with his own grand battle fresco. Leonardo's painting disappeared. But, of course, it was not forgotten. In the early 1970s, Mr. Seracini, a former medical student studying bioengineering in California, took an art course at U.C.L.A. from one of the leading Leonardo experts, an Italian professor, Carlo Pedretti. In 1975, Mr. Seracini returned to Florence, his hometown, and by chance linked up anew with Mr. Pedretti, who had begun a search for the lost painting, theorizing that it still lay behind Vasari's fresco. It was then, on a scaffolding, that Mr. Seracini, a lowly but enthusiastic assistant, found on a flag in Vasari's painting what he considered a possible sign from Vasari of what lay behind it: the words "Cerca, trova," or "Seek and ye shall find." "I was puzzled, curious," he said. "I said: 'O.K., cool it. Maybe its nothing. Maybe it's a coincidence.' " Mr. Seracini admits that considering the words a clue is not scientific, and though they are friends, Mr. Pedretti dismisses Mr. Seracini's interest in the words. They were a motto for one of the companies in the battle, he said, not some mysterious clue. "We Italians are a little inclined to superstition," he said. That search ended without success in 1977. Mr. Pedretti dropped out of the active hunt. But Mr. Seracini never let it leave his mind as he developed a career using his engineering training and modern equipment to analyze works of art. His most contentious finding also landed him his unwelcome place in "The Da Vinci Code." In 2001, he proved that the paint in Leonardo's "Adoration of the Magi" was not applied by the master himself but much later, and as Mr. Seracini said at the time, by someone who was "not even a very good artist." In 2000, Mr. Seracini took up work on the Anghiari painting again, using radar and then thermography on the walls. Two years later, he discovered a tiny crevice behind that panel. In short, Vasari may have preserved the Leonardo by building a wall for his own fresco an inch or so away from the original wall. "Why would you destroy it when you knew it was done by Leonardo and it was still visible?" Mr. Seracini said, adding that Vasari had similarly preserved works by lesser artists. In 2002, his work was frozen, and this being Italy, it is not entirely clear why. Mr. Seracini chalks it up to local politics that he prefers not to discuss. But late in 2006, the nation's new culture minister, Francesco Rutelli, ordered the work begun again. The challenge before Mr. Seracini is great. He cannot touch the Vasari, a treasure on its own, and instead must find a way to peer behind it with machines that do not yet exist. He has several theoretical methods, including a machine that would detect the pigment Leonardo used. There are records of the pigments, paid for by the city, of lead white, vermillion and a blue that might be lapis lazuli. "This is a hell of a challenge," he said. "How do you come here with equipment that doesn't exist, solving a problem of seeing through walls without touching anything?" Even if he finds nothing, Mr. Seracini said he had no doubt that his work would be worthwhile, if only from the standpoint of having developed the technology to say whether it is there or not. "I don't have a reason not to find out," he said. "I think it's about time, since I started just 32 years ago." Mr. Pedretti and Martin Kemp, another top Leonardo expert, strongly support the research, though no one is sure what might be found. Vasari himself said the wall on which Leonardo painted was in bad shape even in Leonardo's time. "I think Maurizio's optimism is greater than mine," Mr. Kemp said. "But this is not to say I think that his investigation should not reach its full conclusion. If we stop here it will just be tantalizing." Mr. Pedretti said: "This would be a great thing. I would be happy with just a few square inches."