Since its first recorded appearance in 1996, Tasmanian Devil Facial Tumor Disease (DFTD) has wiped out an estimated 70 percent of the Tasmanian devil population. Scientists considered bacterial, viral, chemical, parasitic, and genetic causes before determining that the animals were afflicted with a form of transmissible cancer. In this interrupted case study, students review the history of the disease and then use their understanding of the scientific method to recreate some of the thinking that scientists used to try to understand DFTD.  In addition to designing an experiment, students review some of the known causes of human cancer, genetic diversity and bottlenecks, karyotypes, and the potential for transmissible cancer to become zoonotic. Students also consider possible methods for containing and eliminating DFTD. Written by undergraduate biology students, the case is suitable for high school and freshman introductory biology classes. A more advanced treatment for upper-division undergraduates of many of the issues presented here can be found in another case study in our collection, "Poor Devils: The Plight of the Tasmanian Devils," by Annie Prud’homme Genereux.