London, 1889. Veronica Speedwell and her natural historian beau Stoker are summoned by Sir Hugo Montgomerie, who has a personal request on behalf of his goddaughter, Euphemia Hathaway. Her eldest brother, Jonathan, heir to Hathaway Hall, was believed to have been killed in the catastrophic eruption of Krakatoa a few years before. But now a man matching Jonathan's description and carrying his possessions has arrived at the Hall with no memory of his identity or where he has been. Could this man truly be Jonathan, back from the dead? Or is he an impostor, determined to gain ownership over the family's most valuable possessions? Veronica and Stoker agree to go to Hathaway Hall to covertly investigate the mysterious amnesiac.