In this article, I explore the challenges and opportunities associated with using ‘informed imagination’ to write a speculative biography of an historical figure. In the process, I problematize the notion of the archival gap, which has been recently romanced by numerous writers, including myself. By citing archival gaps as a justification for creative license, we neglect the fact that all archives are inherently idiosyncratic in ways that invite, perhaps even demand, the use of both speculation and imagination. Here, I make a case for what I am calling the archival overlap. A careful examination of the existing sources, however sparse or abundant, is likely to reveal reoccurring clues that can be used to shape how we image and construct our subjects. Before we consider the gaps we should tend to these overlaps, I argue, using a current work-in-progress case study of the colonial artist Adelaide Ironside to explore how speculation and imagination are intrinsic to these stages of the biographical process.