Edwin Carver is on the run. He has been shot, and he is making his way through the desert away from the Black Pyramid. A sandstorm gives him a little cover, but he soon finds himself right back at the Black Pyramid. He knows he is dying, but he must keep the scarab he is holding from falling into the men's hands. He buries himself in a sand dune and dies.
The Doctor and Sarah are on a tour of Beta Osiris. The Doctor annoys the tour guides and the other passengers with his comments about archaeological methods. At the pyramid, they don't join the guided tour, but instead the Doctor inspects markings on the outside of the pyramid. Sarah trips over something, which turns out to be the dead body of Edwin Carver. The Doctor takes the scarab from him and they contact the authorities.
Sarah decides to go back to the TARDIS, while the Doctor plans to search Carver's hotel room. Neither notice that they are being followed.
At the hotel, the Doctor searches through Carver's belongings, learning that he intended to sell the scarab to Anwar Nazir. As he leaves the hotel, the Doctor is captured.
Sarah notices she is being followed and heads for Carver's hotel. She is just in time to see the Doctor being carried away. She searches the area for an hour, then finally asks a beggar, who gives her information and a card key in exchange for her camera. After she leaves, the beggar's appearance changes and he dematerialises into the vortex.
When the Doctor awakens, he meets Nazir, who asks him for the scarab. The Doctor fakes ignorance, and Nazir leaves him for now, waiting for his men to bring in Miss Smith.
At the Black Pyramid casino, Sarah assumes the Doctor is on the top floor. Before she goes after him, she heads to the basement and disguises herself as a maid, complete with cleaning cart.
On the top floor, she enters a room where five men are playing poker. Her pursuer is one of them, but doesn't recognise her. She cleans for a bit, then tries to go into a closed room but is told to leave it. She goes into the next room, which has a communicating door to the forbidden room. There she finds the Doctor, and she hides when they hear Nazir come in. He claims to have Miss Smith. The Doctor gives him the scarab that he had earlier hidden on Sarah's person.
Nazir leaves, planning to finish off the Doctor later. The Doctor and Sarah follow him to the Black Pyramid. By heading for the true entrance, they are able to arrive just before Nazir and his men of the Cult of the Black Pyramid. Nazir plans to use the scarab, a micro-circuit key, to release Horus from his sleep.
The Doctor tries to warn Nazir off, but he threatens Sarah's life. The Doctor has to let Nazir fit the key into its slot, but when Nazir does, he is disintegrated by psionic energy. The Doctor explains that he carved scratches on the scarab, making it worthless. They examine the sarcophagus and verify that Horus is long dead, his suspended animation equipment having short-circuited.
Psionic energy is about to shower the pyramid, and the Doctor warns off Nazir's men. They all escape the pyramid while energy spews forth from the pyramid.
The Doctor keeps the now useless scarab.
- Beta Osiris was the only moon orbiting Phaester Osiris.
- The Cult of the Black Pyramid worships Horus and denounces Sutekh as a false god.
- The Doctor compares the Beta Osirian archaeologists' methods to those of Earth archaeologists in the 1920s.
- The stories in Decalog are linked by the story Playback, in which psychic Silverman examines various items in the stranger's pockets. For this story, he examines the scarab.