In this case study, two students meet a professor who surprises them by telling them that a biochemically important molecule’s structure has been incorrectly represented in the published literature - in an article in the Proceedings of the National Academy of Sciences, a major biochemistry textbook, and even The Merck Index. The students are challenged to find the nature of the structural errors and correct them. In addition to demonstrating that the technical literature is not without its flaws, the case reviews important concepts related to geometric isomerism and tautomerism.