This case study discusses a possible national security crisis of a terrorist group stealing radioactive materials in an attempt to build and detonate a dirty bomb over a densely populated metropolitan area. Specifically, this case discusses radioactive decay, which has many applications from carbon-14 dating of ancient manuscripts to dating the age of the solar system to radiation sickness. Radioactive decay can be discussed in a number of courses, in physics, chemistry, earth science, health science courses and others. The case study questions cover a range of applications, and instructors can choose a subset of these questions depending on the main interest of their class.