The bodies of over 25,000 of the 60,000 Australians who were killed during the First World War were either unidentified or unidentifiable. The grief of families of the 'missing' was intensified by the lack of certainty regarding their fate. Even into the 1920s, many families clung to the slim hope that perhaps a mistake had been made and their son, brother or husband might still be alive, yet unable to find his way home. The closed psychiatric files of Sydney's Callan Park Mental Hospital have revealed a soldier whose family was informed in 1916 that he was missing, presumed killed, but who 'came back from the dead' in 1928. Unable to identify himself when found wandering and incoherent on the Western Front, he was returned to Sydney and committed to Callan Park for treatment. He was referred to as 'The Unknown Patient'. After twelve years at the asylum, he was finally identified and reunited with his mother, who had never given up hope that her son somehow may have survived the war. Using New South Wales Department of Health archival files, this paper examines the power of grief and memory and the social impact of war through the lens of the story of this Unknown Patient and explores the realities of life within the asylum walls during the 1920s.