This preliminary text in information systems takes the form of a novel about the use of information systems by the UK police. It shows the reader (1) how the different information systems fit together as a whole for a particular organizational type that readers of any age or experience can relate to; (2) use this knowledge to enable an appreciation of the importance of information systems to the organization and, by implication, to any organization; and (3) introduce the various issues, such as user interface, implementation and training, that have to be considered in developing and using information systems in this overall context; whilst (4) doing this in a book that is as short as possible; and (5) engaging even the most cynical reader. It has three main parts: PART ONE looks at how information systems are used in organizations and how they impact on employees day-to-day; PART TWO looks at how older legacy systems can restrict the potential of information systems to the organization; PART THREE looks at the development and implementation of an integrated information systems infrastructure. Reading this book can serve different purposes: (1) It provides a gentle introduction to the information systems domain for those who do not need a deeper knowledge at this time; (2) It provides an introduction to an important sector of organizations for those starting the world of work in any area including, but not limited to, information systems; (3) It can be used as a prequel to studying a specific topic in the subject area as a way of understanding where that topic fits in to the general picture. (4) It can be used as a prequel to a general course in information systems. The last chapter mentions some newer topics that might be covered in depth on the course as well as building on some of the more standard topics discussed in the text previously. The book can also be regarded as a companion volume to The Adventures of an IT Leader, R. D. Austin, S. O'Donnell, and R.L. Nolan (Harvard Business Press) which I fully recommend. In the main, that text takes the chief information officer's (CIO) perspective and emphasizes his role in the organization. The Information Systems Mystery, on the other hand, takes the perspective of a new recruit starting at the operational level of an organization and follows his adventures over a period of over three years as he first uses police information systems and then plays a role in determining future information systems developments. This text has been designed so that there is little repetition between the two texts. For most people, it would work best if this text is read prior to the CIO one.David Avison is Distinguished Emeritus Professor of Information Systems at ESSEC Business School, near Paris, France. He joined ESSEC in 2000 after being Professor at the School of Management at Southampton University. He has also held posts at Brunel and Aston Universities in England, and the University of Technology Sydney and University of New South Wales in Australia, and elsewhere. He was President of the Association of Information Systems (AIS) for 2008-9. He was founding editor of Information Systems Journal, rated as a 'core' international research journal in information systems. So far, twenty-five books are to his credit and he has also published a large number of research papers in learned journals, edited texts and conference papers. David received the LEO Award for lifetime exceptional achievement in San Francisco in December 2018 having preciously been awarded the International Federation of Information Processing (IFIP) Silver Core and Fellowship of the Association for Information Systems (AIS).