This diverse collection of essays and testimonies challenges critical orthodoxies about the twenty-first century boom in immersive theatre and performance. A culturally and institutionally eclectic range of producers and critics comprehensively reconsider the term 'immersive' and the practices it has been used to describe. Applying ecological, phenomenological and political ideas to both renowned and lesser-known performances, contributing scholars and artists offers fresh ideas on the ethics and practicalities of participatory performance. These ideas interrogate claims that have frequently been made by producers and by critics that participatory performance extends engagement. These claims are interrogated across nine dimensions of engagement: bodily, technological, spatial, temporal, spiritual, performative, pedagogical, textual, social. Enquiry is focussed along the following seams of analysis: the participant as co-designer; the challenges facing the facilitator of immersive/participatory performance; the challenges facing the critic of immersive/participatory performance; how and why immersion troubles boundaries between the material and the magical.