In this factual case study, revelers at a Burns Day celebration in Scotland become ill. When E. coli is suspected, health officials conduct a medical manhunt to discover its source. They and researchers move cautiously from one possible cause to the next—the food served, the water drunk, improper food handling. When none of the investigations prove conclusive, suspicions mount that the microbe was probably passed on by someone sitting at the table where people became ill. During the program, researchers working on the case trace the evolution of the deadly 0157 E. coli strain from animals to ancient humans, and make connections between E. coli and diseases including flu and tuberculosis. (26 minutes)