Night Train to Memphis — Elizabeth Peters

An assistant curator of Munich's National Museum, Vicky Bliss is no expert on Egypt, but she does have a Ph.D. in solving crimes. So when an intelligence agency offers her a luxury Nile cruise if she'll help solve a murder and stop a heist of Egyptian antiquities, all 5'11" of her takes the plunge. Vicky suspects the authorities really want her to lead them to her missing lover, the art thief and master of disguises she knows only as "Sir John Smythe." And right in the shadow of the Sphinx she spots him ... with his new flame. Vicky is so furious at this romantic stab-in-the-back, not to mention the sudden arrival of her meddling boss, Herr Dr. Schmidt, that she may overlook a danger as old as the pharaohs and as unchanging ... a criminal who hides behind a mask of charm while moving in for the kill.