This paper describes implementation research of an intervention in a complex HIV prevention randomised trial in southern Africa. Researchers collected stories of change attributed by 106 community members to an audio-drama edutainment intervention in 41 sites in Botswana, Namibia and Swaziland. The team analysed themes in the stories following a behaviour change model of conscious knowledge, attitudes, subjective norms, intention to change, agency, discussion and action (CASCADA). Storytellers attributed positive changes to the intervention in the areas of gender violence, multiple sexual partners, transactional and intergenerational sex and condom use. Their stories illustrate each of the steps in the CASCADA behaviour change model. As well as supporting an enabling environment for other interventions in the trial, the audio-drama also helped some participants to make personal changes. Collecting and discussing the stories were encouraging for the trial fieldworkers. Documenting the experiences of participants and framing the analysis of stories in an explicit behaviour change model allowed us to reflect on potential mechanisms and pathways through which the intervention impacts on individuals and communities. It helped in the design of the quantitative instruments to measure intermediate outcomes of the trial.