This interrupted case study investigates the geographic origin of white-nose syndrome (WNS) in little brown bats (Myotis lucifugus). WNS is a devastating fungal disease caused by the fungus, Pseudogymnoascus destructans (formerly known as Geomyces destructans), which has led to the death of over 5 million bats in the United States since 2006 and continues to spread. Specifically, the case uses the scientific process to dissect the Warnecke et al. (2012) study published in the Proceedings of the National Academy of Sciences suggesting that the strain of P. destructans causing WNS in North America is an invasive fungal species from Europe. The case format focuses on scientific process skills, such as developing hypotheses, designing experiments, and drawing and interpreting quantitative data. The case also provides an opportunity to discuss coevolution and the evolutionary "arms race" that can occur when a host species evolves resistance to a disease and then the pathogen evolves new ways to infect the host. The case was developed for a non-majors undergraduate biology course but could also be used in any level of college biology or potentially advanced high school biology.