The present volume contains the proceedings of an international colloquium that dealt with heavily fragmented texts and hypothetical sources, and the "shadowy" characters and movements they feature. These two aspects are combined and studied to ascertain how they have been handled in the history of research, to find out what they reveal about the community or the group expressing itself through (or hiding behind) them, and to establish the role these documents and figures or groups should be given in reconstructing an overall picture of developments in the theology and religious life of early Christianity. As can be imagined, such documents and sources have sometimes been taken as an open invitation to come up with all sorts of highly creative exegesis, adventurous reconstructions of texts and movements, and quite daring suggestions about identifying particular groups or presumed literary influences between documents. The essays contribute to the writing of a critical history of researching these types of documents and movements.