The Weapon That Saves Lives opens with a narration that sets the stage for a remarkable journey through the history of medicine, focusing on the discovery of sulfur drugs. The story begins with the character of Oriolus Theophrastus von Hohenheim, known as Paracelsus, who dedicates his life to freeing medicine from superstition and corruption. The narrative then shifts to the mid-19th century, where a young chemist, William Henry Perkin, embarks on an Easter holiday project that leads to the creation of the first aniline dyes from coal tar.