Les Milne was a consultant anesthesiologist, and his wife, Joy, typically found that he came home smelling of anesthetics, antiseptics and blood. But he returned one August evening in 1982, shortly after his 32nd birthday, smelling of something new and distinctly unsavory, of some thick must. From then on, the odor never ceased, though neither Les nor almost anyone but his wife could detect it. For Joy, even a small shift in her husband’s aroma might have been cause for distress, but his scent now seemed to have changed fundamentally, as if replaced by that of someone else. Les began to change in other ways, however, and soon the smell came to seem almost trivial. It was as if his personality had shifted. Les had rather suddenly become detached, ill-tempered, apathetic. It was not until much later that he would be diagnosed with Parkinson’s disease. The scent Joy had noticed would become a possible solution for earlier diagnosis.