When thrift-store aficionado Julie discovers a series of antique paintings with hidden glowing images that are only visible in the dark, she wants to learn more about the artist. In her search, she uncovers a century-old romance and the haunting true story of the Radium Girls, young women who used radioactive paint to make the world's first glow-in-the-dark products—and ultimately became radioactive themselves. As Julie’s obsession with the paintings mounts, truths about the Radium Girls—and her own complicated relationships—are revealed. But will she uncover the truth about the luminous paintings before putting herself and everyone she loves at risk?