Emily and Alexander are with cousin Anwar on an expedition with archaeologist Petrie in Egypt. They are looking for the treasury of the pharaoh Kamose and his friend Ohtep, the mouse pharaoh. The expedition has to hurry to find the chamber because the dam on the Nile is slowly flooding the tomb. The daughter of Petrie's helper, Rabia, sets off with the mice in search of the treasure, because she wants to prove that girls in Egypt are good for more than just cooking and cleaning.