Guardian of the Horizon

I liked this book written by Elizabeth Peters. A previously missing journal from Amelia Peabody is discovered and covers the 1907-1908 season. While staying at their summer home in Kent, England, they are visited by a mysterious messenger who claims that a malady has hurt his family. They travel to Sudan to explore the Lost Oasis, where the Meroitic civilization once thrived. This is the 16th novel in the series.