This directed case study follows the story of “Beaker,” a female corgi who is diagnosed with a urinary tract infection. Students consider the difference between eukaryotic and bacterial cell structures, sizes, and metabolic strategies as they learn that Beaker’s infection is caused by E. coli. As Beaker’s physiological symptoms are revealed, students review innate and adaptive immune responses and discuss ligand-receptor interactions in the context of endocrine signaling. As Beaker is prescribed an antibiotic (amoxicillin) to treat her infection, students uncover how drug-target affinity and specificity are determined by molecular shape and polarity, and they apply these concepts to both mechanisms of antibiotic action and resistance. At the conclusion of the case, students transfer what they have learned to better understand a less commonly prescribed antibiotic of their own choosing. The case was designed for introductory or mid-level biology students to serve as a capstone activity incorporating aspects of bonding, polarity, central dogma, cellular structures, signaling, homeostasis, and immune response.