Decades ago, 3M knew that harmful "forever chemicals" (PFAS) had seeped into the public's blood but kept it secret. These human-made chemicals, used in nonstick pans, food packaging, mascara, firefighting foam, and stainproof fabrics, do not break down in the environment or body. They are now found in nearly every person on Earth and linked to developmental, immune, thyroid, liver, hormonal issues, cancer, and obesity.

Sharon Lerner investigated for 10 years, uncovering that 3M knew of the toxicity since the 1970s. A former 3M scientist who worked in the environmental lab in the 1990s and handled highly sensitive data eventually came forward after a 27-year career, revealing internal knowledge that could have prevented the planet-altering disaster. Lerner sought to understand how a company with thousands of employees concealed such a widespread secret for so long.