This directed case study focuses on the structure, function, and diseases of the circulatory system. A college student and her grandmother “Nonny” face a significant health scare involving the heart. While Nonny is in the hospital waiting for the results of medical tests, she has questions about the workings of the heart that her granddaughter tries to answer based on her knowledge of human biology learned in a class she took in college. The case study is broken into four sections, the first three focusing on a different topic related to the circulatory system (structure, electrical control of heartbeat, heart attacks). The last section ends with a diagnosis that requires students to use reliable web sources to learn more about a particular disease. This case was developed for a non-majors human biology course, but could also be used in introductory anatomy and physiology or high school AP biology.