Finn Ryan, the daughter of a renowned archaeologist, flies to Africa to join Dr. Adamson's excavation expedition in the Libyan Desert. Along the way, she visits the City of the Dead in Cairo, where she is attacked by a huge man with a sword. Finn is saved from certain death by her fellow traveler, pilot and photographer Hilts. The girl believes that this attack is somehow connected with Adamson’s search for the grave of a Coptic monk, one of the apostles of Christ. Together with Hilts, they carry out aerial reconnaissance over the Sahara, but instead of a grave they find the remains of a military camp, and in it - an ancient Roman medallion on which the name of Lucifer is carved. They understand that this is a fragment of some huge mystery that needs to be solved...