Austin Hall and Homer Eon Flint's 'The Blind Spot' is arguably a groundbreaker in science fiction writing, introducing readers to the concept of parallel worlds. Combining fantasy, adventure with an enthralling mystery, it plays with perceptions of the very framework of reality. Just what is the blind spot? A San Francisco room or a portal into another galaxy, an alternative world, or maybe a link to the past or future? The Blind Spot is an imaginative science-fiction concoction from the early 1920s that has become a cult favourite.