This theoretical paper adopts the point of view of the audience of subtitled films and outlines a theory of subtitles as communicative agents within the participation structures of film reception. Based on examples from three Swiss fiction films -- "Heidi" (2015), "Heimatland" (2015) and "Der Goalie bin ig" (2014) -- the following communicative effects are found and illustrated: uniformity, authorisation, foregrounding, aestheticisation, foreignisation. These effects are conceptualised in terms of Constitutive Communication theory and textual agency (Cooren. 2004. Textual agency: How texts do things in organizational settings. "Organization" 11(3). 373-393. doi:10.1177/1350508404041998), which describe that by communicating with audiences, subtitles animate into being other participants in film discourse and contribute to what viewers take away in terms of characters, stories, the cultural aspects they represent and the source culture(s) from which the text is perceived to communicate.