We present the design of Tableau Machine (TM), an AIbased,interactive, visual art generator for shared livingspaces. TM is an instance of what we call “alien presence”:an ambient, non-human, embodied, intelligent agent. Fromoverhead video in key public spaces, TM interprets itsenvironment, including its human audience, and expressesits interpretation by displaying a sequence of abstractimages of its own design. This paper is a case study in thedesign of an art generator with deep and long-termconnections to its physical and social environment.