In 1965, a team of doctors at Rockefeller University announced what sounded like a miracle—they’d found a treatment for heroin addiction that actually seemed to work.

For nearly two years, the researchers had been running an experiment with a small group of men, aged 19 to 37, who’d been using heroin for several years—and the results were astonishing. Men who’d been transfixed by heroin cravings for years, who had tried to quit before and failed, were suddenly able to return to their lives. One started painting. Another finished high school and got a scholarship to go to college.

The key to these transformations was a drug called methadone. But the treatment was controversial, and one of the doctors on the team already had a bit of a reputation as a bold, and possibly even reckless, defier of convention: Marie Nyswander.

This season, we bring you her story and the radical treatment that would upend the landscape of addiction for decades to come.