Nuclear physicist Professor Philip Mortimer wants to spend his holidays in Cairo with his trusty servant, Nasir, and meet with his old friend, Professor Ahmed Rassim Bey, who offers him the opportunity of satisfying his passion for Egyptology. Invited to take part in deciphering Bey's latest discoveries - in this case, some papyrus coming from mummies of the Ptolemaic age - Mortimer soon realizes that one of the fragments deals with the "Chamber of Horus," a fabled crypt that could contain priceless treasures!