Professor Philip Mortimer has decided to spend his holidays in Cairo with his trusty servant, Nasir. There he plans to meet an old friend, who offers him the fantastic opportunity of satisfying his passion for Egyptology - to take part in the deciphering of some recently discovered papyrus coming from mummies of the Ptolemaic age. They soon discover that one of the fragments deals with the Chamber of Horus - a fabled crypt that could contain priceless treasures...