Unlike nineteenth-century Gothic fiction, which tends to fixate on the past, the haunted and the ghostly, early weird fiction probes the very boundaries of reality - the laws and limits of time, space and matter. Here, unimaginable terrors lurk in hitherto unknown mirror dimensions, calamities in ultra-space threaten to wipe clean all evidence of our universe and experiments in non-Euclidean geometry lead to sickening consequences.