This case study is targeted to the middle school science student and written especially with female students in mind. Using an interdisciplinary approach, it combines content from physical science and areas of biology (bacteriology, pathology) to tell the story of Angelina "Fannie" Hesse and her credited, yet not well-known, contribution of agar to the laboratory. Told through an invented recreation (the true details of the story are unknown), students review the fundamental phases of matter with a focus on melting points. The importance of a melting point is linked to the ability to grow and study bacteria in the lab, leading to important discoveries such as those related to infectious disease. A laboratory activity is included, and two versions of Part III are included to give instructors flexibility. By working through the case students should develop a deeper appreciation for how concepts in physical science are related to endeavors such as understanding and curing infectious disease.