Case studies hold great potential for engaging students in disciplinary content. However, little is known about the extent to which students actually cover the problem space afforded by a particular case study. In this research, we compared the problem space afforded by an instructional design case study with the actual content covered by 16 graduate students participating in an online case discussion. In addition, we examined prompts used by two instructors to both widen and deepen that coverage. Results showed that 86% of the afforded problem space was covered during the week-long discussion, although problem-space components were not covered equally. To keep students focused on relevant case details, the instructors used a variety of prompts, accounting for 15% of the total postings. Implications for research and practice are discussed including ways to use case mapping as both a teaching and analysis tool.