For most of his adult life, Ludwig van Beethoven endured gut-wrenching abdominal spasms, severe mood swings and a profound sense of isolation magnified by his growing deafness. Until his death in 1827 at 56, the sublime German composer begged doctors to find the source of his agony. Now William J. Walsh, an expert in the chemical analysis of hair, may have untangled the mystery of Beethoven's suffering and death: lead, in a concentration 100 times the levels commonly found in people today. "Normally, I don't think it's proper to poke around in people's relics to discover their secrets," says Walsh, 64, who tested eight strands of Beethoven's hair at the Health Research Institute outside Chicago. "But he asked specifically that his family and friends discover what had been making him so miserable."

Walsh's findings put to rest earlier speculation that mercury poisoning—possibly from treatments for syphilis—killed Beethoven. But how did he accumulate such high doses of lead? At that time, before its toxicity was recognized, lead was widely used in producing ceramics, glass, paint and even medicines. But for now, scholars are reluctant to offer a definitive explanation for the extremely high level found in Beethoven's hair. "It's all guesswork," says Walsh.

The biochemist was brought into the case by Nogales, Ariz., urologist Alfredo Guevara, a Beethoven lover who bought the 582-strand lock of hair from Sotheby's in London for $7,300 six years ago. There is talk that fragments of Beethoven's skull may also become available for scientific analysis. Says Ira F. Brilliant, founder of San Jose State University's Center for Beethoven Studies: "Be patient. It's an exciting story—and it's not finished yet."