This article investigates the relations between the narratological concept of transfictionality and the trendy phenomenon of transmedial storytelling. Made popular as a concept by Henry Jenkins (2006), transmedial storytelling is the creation of a storyworld through multiple documents belonging to various media. The three fundamental operations of transfictionality—expansion, modification, and transposition—are investigated in terms of their potential for transmedial storytelling. After an analysis of the variety of documents that make up the storyworld of Alpha 0.7 (Südwestrundfunk 2010), a German transmedial story system that comprises a TV miniseries, radio plays, fictional web pages, and links to nonfictional texts created independently of the project, the article asks under which conditions an alternate reality game (ARG) could be added to the system without spoiling the experience of those people who limit their exploration of the storyworld to watching the TV show. In turn, the last section asks what kind of stories lend themselves to transmedial projects and why such projects are currently popular.