Guardian of the Horizon — Elizabeth Peters

A hitherto lost journal of the indomitable Amelia Peabody has been miraculously recovered: a chronicle from one of the "missing years" -- 1907 -- 1908 -- shedding new light on an already exceptional career, a remarkable family . . . and an unexpected terror.

Ousted from their most recent archaeological dig and banned forever from the Valley of the Kings, the Emersons are spending a quiet summer at home in Kent, England, when a mysterious messenger arrives. Claiming to be the teenage brother of their dear friend Tarek, prince of the mysterious Lost Oasis, the charismatic herald brings troubling news of a strange malady that has struck down Tarek's heir and conveys his brother's urgent need for help only the Emersons can provide.

Driven by loyalty -- and a fear that the evil forces opposing Tarek's rule will now exploit the royal heir's grave illness -- the family sets off in secret for the land time forgot -- a mountain fortress from which they narrowly escaped ten years before. Braving the treacherous desert climate on a trek fraught with danger at every turning, guided only by a crumbling map, the Emersons are unaware that deception is leading them onward into a nest of vipers -- where a dreadful fate may await. For young Ramses, forced to keep his growing love for the beautiful Nefret secret, temptation along the way may prove his ultimate undoing. And a dark past and grim obligation have ensnared Nefret once again, as she is helpless to save those she loves most from the prison of the Lost Oasis.