Amy Lindberg spent 26 years in the Navy and she still walked like it—with intention, like her chin had someplace to be. But around 2017, her right foot stopped following orders. Lindberg and her husband Brad were five years into their retirement. After moving 10 times for Uncle Sam, they’d bought their dream house near the North Carolina coast. They had a backyard that spilled out onto wetlands. From the kitchen, you could see cranes hunting. They kept bees and played pickleball and watched their children grow.

But now Lindberg’s right foot was out of rhythm. She worked hard to ignore it, but she couldn’t disregard the tremors. And she’d started to misplace words and thoughts, especially when she got excited. Was this normal? She was 57, fit and clean-living. Could the culprit be menopause?

The diagnosis took all of five minutes. Lindberg had Parkinson’s disease, the neurologist said, with all the classic symptoms. PD—as the scientists she would meet call it—is a neurological disorder, and a life sentence. Sufferers gradually lose control of their muscles, their bowels, their esophagus. Doctors told Lindberg that there was no way to know what had caused it.