This book is a series of snippets and clinical problems which use case vignettes and short case histories in the form of puzzles to encourage the student to gather relevant information and come to a clinical diagnosis. Clinical case scenarios are buttressed with patient stories and include laboratory and imaging data when applicable. Many puzzles are made more compelling by including historically relevant facts and fascinating factoids. Humour, human interest, and pathophysiology come together in intriguing mysteries that help the student practice diagnostic reasoning in a fun, engaging manner. The puzzles are based on internal medicine and subspecialties, including diabetes, endocrinology, toxicology, infectious diseases, hematology, neurology, gastroenterology, and many more. Undergraduate and postgraduate medical students may use them as a fun way to revise and relax. For medical college faculty, the book presents a relevant, relatable method to teach pathophysiology and clinical reasoning.