Pat Barker's First World War novel Regeneration concludes with an author's note remarking that ‘[f]act and fiction are so interwoven in this book that it may help the reader to know what is fictional and what is not’ (251). Taking Barker at her word, this article traces and unpicks the historical source material that she used in her imaginative reconstruction of the life of the military psychiatrist W. H. R. Rivers between July and November 1917. Recuperating the past is simultaneously both the project of the work, as a historical novel, and of the characters, who are engaged with trying to come to terms with their war experience while in a psychiatric hospital away from the fighting. This novel is self-consciously engaging with the issue of how we can access and interpret the past from the present. Furthermore, it engages with the question of what a literary narrative can do with the material traces of the past that historical modes of narration cannot. Exploring Barker's use of a variety of sources – Rivers's published writings, obituaries, and memoirs by those who knew him – reveals that Regeneration is a highly complex palimpsest of source material and fictional intervention, which is designed to explore the historical Rivers's life, while also exploring the ontological, ethical, and aesthetic limits of the historical novel's access to the past.