It is almost 20 years since the idea of dark tourism was introduced into tourism studies, which was still predominantly viewed as a fun-based activity with a potential for a beneficent cross-cultural understanding. The suggestion that it could have dark attributes was both novel and shocking. Once introduced, the idea offered new insights into the tourist experience. It promised to open up new connections with many facets of human sensation and behaviour and also an intellectual framework to assist the management of multi-used tourism sites. This paper will examine the promise of the idea as it evolved through the work of numerous scholars who developed and refined the concept and discovered new applications for it and will explain how the focus, which initially was to identify and catalogue dark sites, has shifted towards the motivation, subsequent experience and consequent behaviour of the tourist in relation to the sites.