Innovative professionals rely on a specific ways of thinking to solve the nonstandard problems that come up in practice (Goodwin, "Am Anthropol" 96(3):606-633, 1994; Schön, "The Reflective Practitioner: How Professionals Think in Action," 1983; "Educating the Reflective Practitioner: Toward a New Design for Teaching and Learning in the Professions," 1987; Sullivan, "Work and Integrity: The Crisis and Promise of Professionalism in America," 1995). "The Professions have Reproductive Practices for Transmitting These Ways of Thinking, Such as Practica" (Schön, "Educating the Reflective Practitioner: Toward a New Design for Teaching and Learning in the Professions," 1987). In this paper, we examine the learning relationship between a mentor and team of college students through an ethnographic study of a game design practicum at a European arts school. To examine the role that the mentor played in this practicum, we use two theoretical constructs. Epistemic frames--the configurations of the skills, knowledge, identities, values, and epistemologies that professionals use to think in innovative ways--provide a model for examining professional expertise (Shaffer, "Comput Educ," 46(3):223-234, 2006a). "Epistemic Network Analysis" (ENA) (Shaffer et al., "Int J Learn Media," 1(2):33-53, 2009) is a method for quantifying changes in epistemic frames (Shaffer, "The Bicycle Helmets of "Amsterdam": Computer Games and the Problem of Transfer," 2010). Our results here suggest that the mentor leads the team on a path that illuminates the nature of learning to think professionally, as well the function of a mentor in that process. We argue that the mentor, rather than providing a direct map to a professional vantage point, scaffolds aspects of the epistemic frame of game design that, in turn, aid in the development of a more professional frame. Using ENA to understand the way that mentors help coach learners to develop epistemic frames should be useful for further studies of professional education, as well as for studies of apprenticeship-based programs for youth.