In this article, we examine young children's narrative play as posthuman, collaborative composing assemblages. Thinking with Tsing (2015), we re/consider collaboration as that which benefits from contamination and unruly edges as lively and generative places can help educators to notice and nurture that which easily goes unnoticed. We are guided by the question of what could be learned about generating literacy learning opportunities for young children in an outdoor program focused on setting up conditions for collaborative, narrative play. Posthuman perspectives deriving from the philosophical work of Deleuze and Guattari, often utilize the concept of the rhizome. However, following the scholarship of posthuman philosopher Anna Tsing and mycologist, Merlin Sheldrake, we turn to another more-than-human lifeform and introduce the construct of mycelial networks for posthuman literacy studies. For this study of children's collaborative composing, we work with Tsing's concepts of unruly edges and contamination as collaboration and introduce the concept of the in/visible. Taking up Tsing's invitation to think differently about the construction of knowledge practices, we map and examine children's collaborative storying by providing two vignettes, which together, comprise a rush of troubled stories. The troubled stories were part of an awakening for program facilitators, a space of four weeks in which they came to see that by attuning to the liveliness of the children's movements, their understanding of collaborative narrative play was transformed. As relations between the human children and facilitators and the more-than-human vividly animate in this study, the in/visible moments that erupt along the interface between the domesticated and the wild can guide educators in planning and enacting young children's literacy learning. To foster children's collaborative composing, we assert, it is necessary to trust that storying occurs, for many children, in the underground, in/visible spaces that underpin the stories they play.