At dawn tomorrow this city will weep tears of blood.
— Marshal Tavannes
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, Catherini 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 descendent 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.
- 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.
- 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
- 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.
- Historical-Domain Character: Charles IX, Catherine de Medici, Admiral de Coligny, ...
- Identical Granddaughter: Sort of.
- 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.
- Oop North: Dodo has a Manchester accent.
- The Good Old British Comp: Dodo is in school uniform when she enters the TARDIS.
- What The Hell, Doctor?: Steven after they escape the Massacre.