In the nineteenth century darkness became visible in the English theatre. To know how this is so, one must glimpse the word “darkness” in its own shadow, its dimmest connotations. “That which hides or is hidden” is the root sense of “darkness,” but it is cognate with words meaning “to trouble or disturb.” The scene (in both spellings) will draw heavily on the unseen for its effect, and the darkness of the theatre resides in its capacity to both hide and reveal that which disturbs, playing always with the paradox of light and darkness, trouble and freedom from trouble, in such a way that darkness itself can become entrancing, an attraction, while the light(ed) repels or pales into insignificance. The theatre both chases troubling reality away from the brightly illuminated stage and gives centrality to the darkness at the focal point of the spectacle—that internal, infernal essence that Milton, in his portrayal of Satan's realm, termed “darkness visible.” A combination of circumstances during the nineteenth century brought dark phenomena to the fore in theatrical representations, first within the marginal exhibition halls and later on the legitimate stage. This essay will trace out one network of historical associations within that development.