In 1911 Egypt, Archaeology Professor Marcus Scarman (Bernard Archard) is excavating a pyramid and finds the door to a burial chamber inscribed with the Eye of Horus. His Egyptian workers flee in terror as he enters the chamber, the eye begins to glow, and he is hit by a green light.
The Doctor, intending to land the TARDIS at the UNIT base, ends up in the sealed wing of an English estate called the Priory. Sarah Jane sees an animal apparition. The time-travellers are found by the butler, soon to be dead, who tells them they are on the Scarman Estate, which has been taken over by an Egyptian named Ibrahim Namin (Peter Mayock). He claims to represent Scarman, but Scarman’s friend Doctor Warlock (Peter Copley) confronts him. Namin sends a robot dressed like a mummy after him and the time-travellers, but they escape to a hunting lodge used by Scarman’s brother Laurence (Michael Sheard). He has a Marconiscope which has intercepted a mysterious signal from Mars, which the Doctor decodes as “Beware Sutekh.” Sutekh was the last of a powerful alien race called the Osirans.
Namin and the mummies greet the arrival of Sutekh’s servant, who travels via a spacetime tunnel portal disguised as a sarcophagus. Namin is killed by the servant, who turns out to be Marcus Scarman himself, or at least his corpse animated by Sutekh’s will. Scarman and the robots secure the estate and begin constructing an Osiran war missile aimed for Mars, intended to free Sutekh from the prison Horus sealed him into millennia ago. The Doctor disrupts the tunnel by tossing in the TARDIS Key (Who knew?) and steals Namin’s ring from his corpse.
Sarah suggests they simply leave in the TARDIS, as the world did not end in 1911. The Doctor shows her 1980 and a blasted Earth. Laurence, who is along for the ride, is astonished by the TARDIS and everything else. Back in 1911, the Doctor creates a jamming unit with Namin’s ring to break Sutekh’s hold over his animated servants, including Scarman, but the robots overrun the hunting lodge. The Doctor decides to blow up the unfinished rocket—Sarah Jane’s idea. To this end, they obtain gelignite from a poacher’s hut. Laurence tries to help his brother but is killed. They set off the explosion using a rifle fired by Sarah (when did she learn this skill?), but Sutekh has the telekinetic power to smother the explosion, so the Doctor uses the time-tunnel to reach Sutekh and break his control. The explosion takes place, but Sutekh takes control of the Doctor and sends Scarman to the Pyramid on Mars.
The Doctor breaks free and follows Scarman, along with Sarah, through a series of locked chambers, solving logical puzzles set up by the Osiran jailers. In the end, Scarman decays to dust, but Sutekh is freed and is coming to Earth. The Doctor uses a module from the TARDIS to attack Sutekh in the space-time tunnel, aging his body 11,000 years. The Priory is consumed by flames—later, the UNIT base will be built on the ashes—but the Doctor and Sarah Jane escape in the TARDIS.
The Priory was played by the Gothic Revival Stargroves Estate in Hampshire—Mick Jagger’s house at the time. The story was highly praised and has always been considered one of the best, particularly for its Gothic Horror trappings, largely borrowed from various Mummy movies, though unfavorably compared at times to Stargate, which used the Egyptian motif quite effectively. To my mind, it kicks off the best period of the early Doctors, when Philip Hinchcliffe and Robert Holmes, in charge of scripts and inspired by Hammer Films, joined with the genuinely strange Tom Baker and some remarkable companions to create a series of stories with a Gothic Victorian atmosphere, darker cliff-hangers, and macabre humor, set in believable alien worlds with imaginative set-design.