Doctor Who/Recap/S14 E1 The Masque of Mandragora

"The Doctor: Humans have got such limited little minds. I don't know why I like you so much.

Sarah Jane Smith: Because you have such good taste.

The Doctor: That's true. That's very true."

The TARDIS pitches up in Renaissance Italy, having had an encounter en route with a fizzy ball of energy that the Doctor calls the Mandragora Helix. He hasn't realised that he's brought it with him, and when it escapes from the TARDIS and begins taking over or killing the locals, he follows.

The energy finds an underground temple and takes over the Cult of Demnos which is led by court astronomer Hieronymous, instructing them to prepare the way for Mandragora's full appearance. However, the astronomer himself is a pawn in political intrigues between Count Frederico and his cousin Duke Giuliano. Giuliano has just acceded to the Duchy of San Martino and a grand Masque will be held in honour.

During the dance, the Cult of Demnos attack the court and kill many, while Hieronymous - now unified with the Mandragora Helix - confronts the Doctor in the underground temple. Attempting to blast the Doctor with pure Mandragora energy, he is foiled when the Doctor reveals he has earthed both himself and the altar: the energy is drained off and the earth is safe.

Early in the story, Sarah becomes the first companion to question how come she can understand and be understood when the locals must all be speaking Italian. The Doctor says it's a "Time Lord gift", and it's later explained that it's done telepathically via the TARDIS.

Tropes:

 * Beard of Evil: Hieronymous has a glorious beard.
 * Black Cloak: The cultists wear these, but Hieronymous opts for the pimp purple cloak and gold bling medallion seen in the image above.
 * The Blank: Hieronymous after absorbing the Mandragora Helix.
 * Blue Blood
 * Bound and Gagged: Sarah Jane
 * Brainwashed and Crazy
 * Chosen One
 * Cold-Blooded Torture
 * Cool Mask: The cultists' gilded masks, especially the one Hieronymous wears.
 * Cult
 * Damsel in Distress
 * Did Not Do the Research: The Duke thinks that the earth not being flat is a new and radical idea. Geocentrism doesn't work without a round earth.
 * Dragon with an Agenda: Hieronymous
 * Energy Beings: The Mandragora Helix.
 * Evil Laugh
 * Evil Uncle: Count Federico
 * Human Sacrifice
 * Masquerade Ball: The Cult of Demnos takes advantage of Giuliano's swanky ascension party to conceal themselves in Part 4.
 * The Mole
 * Not Herself: The Doctor knows Sarah has been taken over...because she's the first companion to ask how come she can understand people who speak other languages. Err, right...
 * Reasonable Authority Figure
 * The Renaissance: Takes place in the late 15th Century.
 * Religion of Evil: The Cult of Demnos
 * Royally Screwed-Up: Count Federico. He has Giuliano's father killed to bring him one step closer to becoming the Duke of San Martino, but ends up being unable to have Giuliano assassinated.
 * Secret Circle of Secrets
 * Smug Snake: Both Federico and Hieronymous are arrogant would-be tyrants, but both are also convinced that they have more control over the situation than they do; Federico is so consumed with his schemes to overthrow his nephew that he ignores the real threat (the Cult of Demnos and the Helix) until it's too late; similarly, Hieronymous is a deluded fraud trapped by superstition and seduced by dreams of glory who ends up utterly consumed by the Helix.
 * Sword Fight
 * Tap on the Head
 * Translator Microbes
 * Unwilling Suspension
 * When the Planets Align
 * The Wise Prince: Giuliano
 * The X of Y