In this paper we investigate the Dark Net which is the part of Internet accessible only via special browsers such as Tor. The Dark Net is the home of black-markets for illegal goods and services such as drugs, weapons and fake identities. In this study we investigate the Dark Net as a digital infrastructure over time to address the following research question: what are the forces underlying Dark Net markets? Our empirical approach is based on a set of techniques for accessing Dark Net marketplaces (DNM) and collecting various types of information on sites, transactions and users. We draw also on secondary sources such as reports of police interventions and interviews. Our analysis follows the tradition of critical realism to shed light on the generative mechanisms enabling Dark Net markets to operate and survive.