Based on true events of the late 1920s, teenage sisters Bessie and Jo dream of faraway places while they paint glow-in-the-dark watch dials at the American Radium Factory in New Jersey. When Jo becomes ill, a larger, darker truth begins to emerge: She is not the first girl in the radium factory to become unwell. Bessie fights not only for her sister, but also for the rest of the women around her; she becomes a powerful advocate as she risks everything to stand up to the corporation that provides her family's livelihood.