"Beyond the Wall of Sleep" is a short story from 1919 based on the innovative (at that time) idea of using psychology for explaining real-life issues. Incidentally, a near namesake song ("Behind the Wall of Sleep") appeared on the debut album of Black Sabbath. The second story, "From Beyond" (written in 1920, published in 1934), hovers around the theme of a mad scientist willing to peek beyond reality. It inspired a few films, songs by death-metal bands, and it even features in the PC game, "Half-Life". The last story of the trio is "The Transition of Juan Romero", from 1919. The feature "character" is a mysterious evil encountered in an ancient ritual to the Mexican deity, Huitzilopochtli.