London has harbored many curious characters, but few more curious than the artist and visionary Austin Osman Spare (1886-1956). A controversial enfant terrible of the Edwardian art world, the young Spare was hailed as a genius and a new Aubrey Beardsley, while George Bernard Shaw reportedly said "Spare's medicine is too strong for the average man." But Spare was never made for worldly success and he went underground, falling out of the gallery system to live in poverty and obscurity south of the river. Absorbed in occultism and sorcery, voyaging into inner dimensions, and surrounding himself with cats and familiar spirits, he continued to produce extraordinary art while developing a magical philosophy of pleasure, obsession, and the subjective nature of reality. Today Spare is both forgotten and famous, a cult figure whose modest life has been much mythologized since his death. This groundbreaking biographical study offers wide-ranging insights into Spare's art, mind, and world, reconnecting him with the art history that ignored him and exploring his parallel London; a bygone place of pub pianists, wealthy alchemists, and monstrous owls.