In this essay the social historian Simon Featherstone examines the theatre of the Scottish medium Helen Duncan and argues that her strange, illicit performances offer a way of re-reading British popular performance in the 1930s and 1940s. This critically neglected period has been characterized by the decline of the radical energies of nineteenth-century music hall and the variety theatre which displaced it. Duncan's performances, however, with their extravagant display and management of her body and deployment of a range of references to popular materials, including puppetry, melodrama, children's games, and sentimental narratives, suggest the existence of other trajectories. Like the ‘dark village’ that Eric Hobsbawm identified as the illegal shadow of nineteenth-century social practices, Duncan's ‘dark theatre’ can be seen as a shadow world of mid-century performance styles. It provided a knowing yet emotionally fulfilling theatrical experience for her audiences while at the same time posing radical questions about the limits and meanings of the representation of gender and class in the unregulated venues of the spiritualist circuit. Politically ambiguous in their mixture of entrepreneurial exploitation and willingness to offer forthright challenges to social and legal authorities, Duncan's performances indicate the persistence of complex spaces and traditions of popular theatricality in the period.