The author examines two aspects of the case of Fanny Moser (Emmy von N. in the ‘Studies on Hysteria’): first, a hitherto unknown letter written by Sigmund Freud to Fanny Moser's daughter in 1935, in which he revises his diagnosis of half a century before, describing it as ‘a bad diagnostic error’ and apologising to the daughter; second, the dates of Fanny Moser's treatment. All previous attempts have failed to date it consistently. The author combines all the information about the case of Fanny Moser and the circumstances of Freud's life in that period and shows that Freud took over the case in 1888, not in 1889. In addition, he suggests that Emmy von N. has had a significant influence on Freud's papers on ‘Hysteria’ and on his comparative study ‘Organic and hysterical motor paralyses’.