Literary narratives are well recognised for their power to foster engagement with complex social themes. Transmedia narratives, which present the same story in different media, can help advance both critical multimodal discourse studies and multiliteracies pedagogies. To harness this potential, we need to develop methods for systematically relating media affordances to discourse-semantic patterns and the broad social themes these patterns construct in narratives, and ensure these methods build on the knowledge learners bring to the classroom. This article introduces a social (...) semiotic method for analysing transmedia narratives and illustrates its ability to reflect the persuasive power of narrative and build on young children's critical multimodal awareness. This is achieved through a case study comprising data from three adaptations of the same award-winning narrative - animated film (Joyce, W. (Producer), Joyce, W., & Oldenburg, B. (Directors) (2011). The fantastic flying books of Mr Morris Lessmore [Motion Picture]. Moonbot Studios), interactive app (Moonbot Studios. (2011). The fantastic flying books of Mr Morris Lessmore (Version 1.4). [Mobile Application Software]), and traditional-format picture book (Joyce, W. (2012). The fantastic flying books of Mr Morris Lessmore. Illustrations by William Joyce and Joe Bluhm. Moonbot Books) - and mother-child interactions with the book and the app. (shrink)