In its relations with its follow-up on the Web, a TV series such as Lost (2004-2010) is noteworthy for the dialectic established between the viewer's subjec- tion to the narrative thread and his/her liberation through apparently different but closely connected activities of analysis and narration (fanfiction). It was probably to reclaim these virtual spaces of freedom occupied by the public that the producers adopted ARG (alternate reality game), a type of web writ- ing characteristic of viral marketing, as well as the broadcasting of webisodes (short video segments available on the Web), in the framework of what can certainly be called 'transmedia storytelling'?.