This unit challenges high school students to uncover answers for the cause of death of a teenage football player while building an understanding of the role of the urinary system in maintaining homeostasis. The unit first engages students by watching a news clip about the tragic death of a healthy, vibrant young man who died from drinking too much water and Gatorade during football practice. Students then consider the driving question, “If water is necessary for survival, how can such an essential substance kill us?” The unit utilizes a storyline of this phenomenon with four additional phenomena-driven questions that are central to the unit. The phenomena-driven questions are 1) What are the normal components of urine? 2) How is urine made? 3) How is the urinary system controlled/regulated? 4) How does the urinary system interact with other systems to keep an organism alive? The lessons in this unit are structured around the 5E instructional model (Engage, Explore, Explain, Elaborate, and Evaluate), and the lessons outline a number of techniques to deepen student understanding of the concepts in this unit. The focus throughout the unit is not on what students know but how they know what they learn about homeostasis and the urinary system. Students write and share explanations, use teacher models and generate their own models, make claims using evidence they generated from lab activities, and create and show a video of what they have learned. Extensive background and supplemental teacher materials are provided. Teachers are encouraged and supported in techniques for using specific feedback and reflective questioning, allowing multiple attempts at mastery and using criterion-based evidence for assessment. Anecdotal and formative assessments are also included.