Set in 1907–08, the novel begins with the Emersons in England after they have been barred from the Valley of the Kings. Ramses, secretly in love with Nefret, plans to leave for Germany until a visitor carrying a damaged map and an urgent letter draws the family back toward the isolated civilisation they encountered years earlier in the Sudan.
The journey forces Amelia and Emerson to retrace a hazardous desert route while Ramses and Nefret face both external enemies and their unresolved relationship. Within the hidden kingdom, a succession crisis and old obligations place the visitors under suspicion, and escape depends on discovering who summoned them and what has happened to the community since their last departure.