Concept mapping is a research method often used to assess participants' knowledge of a topic. Our project studied how preservice teachers' knowledge of challenging behaviour changes (or not) during their final professional teaching experience. We asked the participants to make a concept map before and after their final professional teaching experience because we anticipated it would (1) provide reflective space for the preservice teachers to think about 'what' they knew about challenging behaviour, without feeling like they were being 'tested' in an interview, and (2) illustrate knowledge change during their final professional teaching experience. However, our use of concept maps was not without trepidation because of the type of knowledge under investigation. Concept mapping to assess an individual's knowledge can be epistemologically rigid because (regardless of the quantitative or qualitative analytic approach used) maps are typically assessed against a 'correct', 'factual' knowledge-base. We, on the contrary, were interested in participants' knowledge of a contentious issue and our theoretical framework supported the existence of multiple knowledges. This case describes how we negotiated the boundaries of existing concept mapping methods to facilitate analysis of participants' understandings of 'messy' knowledge and how this changed over time.