When a gravely ill young woman is rushed to the hospital, doctors make a shocking discovery: she has an "astronomical" amount of lead in her body. What begins as a medical mystery quickly becomes a criminal investigation. Hannah Pettey, a young mother from Alabama, suffered debilitating pain and lost more than 45 pounds in the months prior as her health rapidly declined. Investigators focus on the two people she trusted the most as the police work to uncover who was poisoning Hannah, and why.