This paper reports on an exploratory case study of learner participation within the context of online language learning in virtual world platforms. Data for this investigation was collected through a case study of a Business English course within a qualitative Case-Study Research framework. This study examines learner activity in virtual worlds in relation to three main features of the platform: avatars, artefacts and spaces. The study makes use of "Reflexivity" and "Exploratory Practice" as its core methodological approach to the building of the case. The virtual world data is analysed from a multimodal perspective and makes use of "visualization" as the primary analytical tool. In an attempt to broach the Eurocall 2015 conference topic of Critical Computer-Assisted Language Learning (CALL), this paper will present and discuss three findings: a broadening of our understanding of learner participation in virtual worlds, the critical role played by course designers and teachers in the shaping of learner participation in virtual worlds, and the potential of virtual worlds as a tool for reflective practice and practitioner research. [For full proceedings, see ED564162.]