The Masque of Mandragora is the first serial of the 14th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 4 to 25 September 1976.
The serial is set in the fictional European duchy of San Martino in the late 15th century. In the serial, the astrologer Hieronymous (Norman Jones) seeks to summon the power of an intelligence called the Mandragora Helix to rule the Earth.
Plot
The Doctor shows Sarah some of the TARDIS interior, and they come across the secondary console room. Activating the viewscreen, the Doctor sees a swirl of living energy in the time vortex – the Mandragora Helix, which starts to draw them in. The intelligence within the Helix psychically attacks them as the Doctor tries to pilot the TARDIS through it. The ship ends up inside the Helix, and the Doctor and Sarah duck behind the TARDIS as a fragment of glowing Helix energy flies by. They escape in the TARDIS, not knowing that the fragment has entered with them.
In 15th century San Martino in Italy, a peasant revolt is violently put down by Count Federico and his men, led by Captain Rossini. In a palace, Federico's brother, the Duke of San Martino, lies dying, attended to by his son Giuliano and Giuliano's companion Marco. The Duke's death had been foretold by Hieronymous, the court astrologer, but Giuliano, a man of science, does not believe in such superstition. In fact, Hieronymous is working for Federico, and the horoscope's prediction of the Duke's death was helped along by poison. Hieronymous tells the Count that he feels his powers are growing, but all Federico wants is for the astrologer to foretell Giuliano's death next, and he will take care of the rest.
The TARDIS materialises in a field near San Martino, and when the Doctor and Sarah exit, the energy fragment flies out of the TARDIS, unseen. Sarah wanders off and is kidnapped by a group of men in hooded robes. The Doctor tries to rescue her but is knocked out, and when he awakes he witnesses the energy fragment fly towards and kill a peasant. Searching for Sarah, the Doctor is confronted by the Count's men and arrested.
At the court, the Doctor tells Federico that the energy fragment could spell the end of the world. The Count at first thinks the Doctor is a seer, like Hieronymous, but when the astrologer quizzes the Doctor, it becomes clear that the Doctor does not believe in any of it. Federico orders the Doctor to be executed as a spy. Meanwhile, Sarah is brought before a priest and told that she is the foretold sacrifice to Demnos, the Roman god of moonlight and solstice. In the palace courtyard, the Doctor is led to the executioner.
Before the executioner's sword lands, the Doctor unfurls his scarf and hooks it around the executioner's ankle, throwing him off balance. The Doctor escapes and finds his way into catacombs beneath the city. The guards, fearing the Brethren of Demnos who reside there, stop their pursuit. Inside, Sarah is laid out on an altar. A purple-robed figure is about to stab her when the Doctor snatches Sarah away, just as the fragment appears in the chamber, suffusing it with a red glow and providing a distraction for the two to escape.
Giuliano examines the body of a guard who was killed earlier by the fragment, and while he does not know the cause of the guard's death, he dismisses ideas that it was some kind of fire demon. The Doctor and Sarah are found by palace guards. In the temple, the Helix manifests itself as a pillar of red light and tells the purple-robed figure that he will be given undreamed-of powers to carry out its will on Earth and become the planet's supreme ruler. After the Helix vanishes, the figure removes his mask, revealing the face of Hieronymous.
The guards take the Doctor and Sarah to Giuliano, who shows him the dead guard's body and tells the Doctor of fears that if Federico rules San Martino, all knowledge and learning will be suppressed. Elsewhere, Federico discovers that Giuliano has invited several nobles to San Martino to celebrate his succession to the Dukedom. Angered, Federico demands Hieronymous make up a new horoscope and poison Giuliano before the next evening.