The one where a lot of people die.
Also known as The Massacre of St. Bartholomew's Eve.
The TARDIS materialises in Paris, 1572, and the Doctor wanders off to visit a famous apothecary while Steven falls in with a group of Huguenots (French Protestants) from the household of Admiral de Coligny.
Steven and his new friends rescue Anne Chaplet, a serving-girl, from some guards and hear of a plan by the Queen Mother, Catherine de Medici, to massacre all French Protestants.
Meanwhile, the Abbot of Amboise - a Doppelgänger of the Doctor - is executed by the authorities for failing to have de Coligny assassinated, giving Steven quite a shock when he finds the body in a gutter.
Steven heads back to the TARDIS at the apothecary's shop and the two depart just as the massacre begins. Steven is furious that the Doctor refuses to save Anne from the massacre and storms off once the TARDIS lands again on Wimbledon Common. While he's gone, a girl enters the TARDIS looking for help from the Police. When Steven returns to warn of the approach of two policemen, the newcomer tells him and the Doctor that her name is Dodo Chaplet - a descendant of Anne? The Doctor hits the "dematerialise" button, once again kidnapping a companion. Steven is outraged but Dodo doesn't seem to mind.
- A Day in the Limelight: Not only is this the first serial to feature a single companion, Steven is the central character throughout as, while William Hartnell is present as the Abbot, the Doctor only appears in the first and last episodes.
- Alan Smithee: This story was originally written by John Lucarotti, but script editor Donald Tosh rewrote almost the whole story. Lucarotti demanded his name be taken off the credits, but since the episodes are missing, it's unknown whether his request was granted.
- The Bad Guy Wins / Karma Houdini: Sadly, all too much Truth in Television.
- Beethoven Was an Alien Spy: Steven encounters several of the people involved in the 16th century St. Bartholomew's Day Massacre.
- Blood Knight: Gaston loves a fight. He's constantly trying to provoke fights with Catholics.Gaston: There now. I thought he might be roused, what a pity.Steven: What about the girl? Where is she?Gaston: She's just a servant. A chance to bait a Catholic. Forget her.
- Continuity Cavalcade: After Steven leaves, the Doctor mentions Susan, Ian Barbara and Vicki and how they left him. And then Dodo appears.
- Continuity Nod: Steven says that he's been to Egypt.
- Criminal Doppelgänger: The Abbot. Does result in being-confused-for-each-other shenanigans, but played for drama instead of for laughs.
- Darker and Edgier: One of the darkest Who serials ever.
- Deadly Decadent Court: Yup.
- Downer Ending: The story ends with the Doctor and Steven leaving the St. Bartholomew's Day Massacre while possibly all their friends are murdered, leading to Steven giving a What the Hell, Hero? speech to the Doctor and nearly leaving the Doctor. It is implied at the end that Anne Chaplet could have survived, but thousands were still killed.
- Entertainingly Wrong: Given his track record, it's not unreasonable for Steven to assume the Abbot is in fact the Doctor in disguise. However in this case the Abbot really is another person who happens to resemble the Doctor.
- Fish out of Temporal Water: Steven, very much so. He knows next to nothing about the year he's in. The political and religious climate is very volatile, and it leads to a lot of trouble for Steven, particularly when he's separated from the Doctor.
- Just being English in sixteenth century France puts him on the wrong side of the Catholic faction.
- Foregone Conclusion: When the story has the word "massacre" in the title, you can bet your bum people are gonna drop like flies.
- Historical-Domain Character: Charles IX, Catherine de Medici, Admiral de Coligny, ...
- Identical Stranger: The Doctor and the Abbot of Amboise.
- Kill 'Em All: Most of Steven's allies in the story are historical victims of the massacre.
- Mood Whiplash: The story ends with the darkest sequence of events in the entire series thus far. The Doctor forcibly transports Steven to 1960s London to escape the massacre, abandoning Anne. He rages at the Doctor about how amoral he is and storms out of the TARDIS, leaving the Doctor behind to perform some Thinking Out Loud about how everyone leaves him and he has no control and nowhere to go. This is suddenly interrupted by Dodo accidentally walking in on him, deciding to travel with him in about two minutes of conversation, and then Steven returning with no explanation to suggest that Dodo might be one of Anne's descendants.
- Oop North: Dodo has a Manchester accent.
- Pinball Protagonist: Steven spends the story as main protagonist, but he completely fails to change events in the slightest, and has no real idea what is going on. He only just finds the Doctor in time to escape Paris and avoid the impending atrocity.
- The Good Old British Comp: Dodo is in school uniform when she enters the TARDIS.
- Unbuilt Trope: Steven sees someone who appears to be the Doctor in disguise arranging a Final Solution, assumes that the Doctor must be planning something, ends up unable to save any of the victims due to his misguided attempts to help with whatever the Doctor must be planning, and the real Doctor refuses to save anyone under his belief that history cannot be changed (leading to a What the Hell, Hero? moment and Steven even attempting to quit).
- What a Senseless Waste of Human Life: The actual massacre weighs heavily on the Doctor and Steven.
- What the Hell, Hero?: What The Hell, Doctor?: Steven nearly leaves the TARDIS over the Doctor's refusal to save anyone during the massacre.I tell you this much, Doctor, wherever this machine of yours lands next I'm getting off. If your researches have so little regard for human life then I want no part of it.