Chicago: Shasta Publishers, 1950. First edition. His second story collection. SIGNED by the author as Leinster, and with his real name, William F[itzgerald] Jenkins. Leinster is credited with the invention of parallel universe stories, such as this collection's title story, which first appeared in 1934 in Astounding Stories magazine. Hinges a little darkened, still fine in lightly soiled dust jacket, slightly tanned at spine, and nicked at spine ends and corners.