Preparing to become an effective primary school mathematics teacher is a challenging and complex task; and is influenced by one's past experiences, personal knowledge of, and beliefs and attitudes towards mathematics. This paper examines the experiences of a small group of pre-service teachers who did not pass their first year mathematics education course. As part of their second attempt at this course for a Bachelor of Teaching (primary) degree the pre-service teachers engaged in a mathematical investigation. Data suggests that undertaking an open-ended mathematical investigation facilitated positive shifts with regard to the pre-service teachers' knowledge of, and beliefs and attitudes towards, mathematics. Participation in such investigations appears to have potential for supporting pre-service teachers who have initially experienced difficulties in their journey to becoming effective mathematics educators.