The Masque of Mandragora

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 from 4 September to 25 September 1976.
Plot
The Fourth 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...