Who is Joe Slater from Dagon and Other Macabre Tales and what is their importance?

Joe Slater is a character in the story, Beyond the Wall of Sleep. Joe is an alcoholic, who is in his forties. He lives in an isolated community in the mountains. Over the course of the story, Joe begins to have strange vivid dreams, which eventually lead him to murder a man. As a result, he is committed to a mental hospital.