This study explored how the school classroom context influenced the expression of one prospective science teachers' beliefs about science and science teaching. Using a single case study design, the article presents a case report of Dan, a 31-year-old scientist who decided to become a science teacher after six years as a field scientist with an international science corporation. Personal construct theory and experientialism provided the theoretical frameworks for data collection and analysis. Multiple sources of data were gathered to ensure triangulation. Data sources included field notes made during observations of Dan's student teaching, transcripts from formal and informal interviews with Dan, and document analysis from teaching materials gathered throughout student teaching. Using the constant comparative method of data analysis, four interrelated categories of Dan's student teaching experience were generated: beliefs about teaching science, constrained teaching and instructional conflict, science beliefs and classroom practice, and anticipations of a new beginning. Implications for science education and for teacher development are offered.