Baroness Orczy 
By The Gods Beloved [PDF ebook] 

Mark and Hugh are school friends. Mark has visited Hugh’s house, whose father is an archaeologist and Egyptologist and where there is an odd museum, complete with mummies. One day, Mark receives word from his friend to ’Come at once if you can’. He finds Hugh has taken over his father’s work and is in possession of a secret encoded papyrus that is thousands of years old. He has also discovered that the descendants of ancient pharaohs are still living in the Libyan Desert. The two friends set out at once for Egypt. Their journey involves incredible adventures, strange sights, a beautiful princess and great dangers.