The Unknown Purple is a 1923 stage-play-based, science-fiction genre, silent film, written and directed by Roland West. The film could probably be the first dealing with the subject of invisibility and might have been based upon the novel The Invisible Man by H.G. Wells.
After his release from prison, an inventor develops an eerie purple light that renders him invisible, enabling him to seek revenge on his unfaithful wife and his crooked partner.