This interrupted case study introduces basic modeling to investigate a decline in an American marten population on an island in Southeast Alaska. Two summer field technicians working on a long-term field ecology project for one of their professors notice that there are fewer marten captures this year. Through discussions with their professor, conversations with a local fur trapper, and based on their own observations, they develop a plan to model the population and the potential causes of the decline to solve the mystery. Students use Excel or other database software along with life tables and introductory population ecology to investigate three potential causes of the marten population decline. This case was developed for use in an environmental science or wildlife management course but could also be used in an advanced science high school course or general ecology course. It would be beneficial for students to have some background in statistics including how to interpret R-squared values, p-values, and 95% confidence intervals.