Following the kidnapping of Rima Barton Fu Manchu through Adrian Arden a crooked Cairo attorney offers to exchange Rima for the Mocana Relics. Nyland Smith specifies that the exchange be made that night at midnight in the King's Chamber of the great pyramid of Giza. Fu Manchu stipulates that only Nyland Smith and Dr. Petrie, Barton will be acceptable to him as bearers of the relics. Planning to trap Fu Manchu's agents Smith has a cordon of police around the pyramid and with Petrie and the relics enters the huge monument where a stone door closes behind them trapping them inside...