Emerging diseases and potential pandemics make the news nearly every year. Students (and everyone else) may wonder where new infectious diseases come from, how scientists assess the risk of a pandemic, and how we might go about preventing one. This case study uses a PowerPoint presentation to explore these questions by focusing on HIV, a pandemic that began as an emerging disease. The storyline progresses backwards through time as scientists attempt to unravel the origins of a new, mysterious plague. Much of the case relies on audio excerpts from an episode produced by Radiolab, an acclaimed radio show that explores a variety of topics in science and culture (www. radiolab.org). Students use graphics, animations, and sound clips presented in the PowerPoint slides to discuss several sets of questions. The case is suitable for a wide range of high school and college introductory biology courses, as well as undergraduate microbiology, ethics, and public health courses.