Many of us can be transfixed by a certain something for prolonged periods, but millions of people worldwide are literally overpowered by their obsessions. While some obsessions can bring us pleasure and happiness others can bring nothing but heartache. We reveal what drives some people to take the human pursuits of happiness, thrill seeking and fantasy to extremes, and why others are disabled by persistent fears and endless rituals. This documentary takes a closer look at this fascinating subject and considers some of the scientific treatments currently being explored.