This case study describes the creative processes behind the development of documentary music theatre work A Box of Memories. The musical explores the complex impacts of dementia from the perspectives of the person, their family and a healthcare provider, based on the lived experience of a daughter-father creative team. Documentary music theatre is an interdisciplinary genre that integrates documentary practices with the conventions of music theatre to depict real-life events, experiences, and evidence. This genre is presented as a powerful medium for challenging societal attitudes and beliefs, with the potential to foster social progress and transformation. By documenting the creative process, this article contributes to the discourse on documentary music theatre and offers a framework for creating socially transformative and authentic works. The authors highlight the necessity of practice-based inquiry to expand music theatre research, which has predominantly focused on retrospective analyses of existing productions. By detailing the conceptualisation, writing, design, and rehearsal processes of A Box of Memories, this case study provides a prospective framework for theatre-makers. It offers support for practitioners in authentically engaging with documentary material while advancing meaningful, socially-engaged storytelling.