"Know Thy Neighbor" by Elisabeth R. Lewis is a science fiction story published in the early 1950s. Set in the gritty and unsavory Tenderloin district of San Francisco, the narrative explores themes of paranoia and the unknown lurking within seemingly ordinary lives. The tale draws readers into a world where the everyday mundane becomes intertwined with terrifying supernatural elements, driven by the protagonist's fears and suspicions of her neighbors. The story follows Ellen Tighe, a young woman who feels isolated and uncertain in her dilapidated apartment building. Her unease escalates dramatically when she discovers a dead cat on her fire escape and later encounters what appears to be a ghastly green creature stuck in the incinerator chute. Panicking and unable to convince herself of her sanity, Ellen begins to suspect that her neighbors might not be who they seem, leading her to horrifying conclusions about their true nature. As she grapples with her fears and the possible reality of monstrous beings disguised as ordinary people, the tension mounts, culminating in a chilling confrontation that leaves the reader questioning the safety of familiarity and the deceptive appearances of those around us. (This is an automatically generated summary.)