Following their escapade in the Sense-sphere, the doctor makes yet another attempt to get Ian and Barbara back to their home. When they along with Susan,who admittedly will miss the two teachers, emerge from the TARDIS they find themselves in late 18th century France,specifically July of 1794 during the period of the revolution known as the Reign of Terror. Finding a house in which to remain inconspicuous, they all find themselves swiftly accosted by D'Argenson and and Rouvray,counter revolutionaries and held at gunpoint when some of the fake papers they locate in the home bare the signature of Robespierre,chief government orchestrator of the French government. Revolutionary soldiers discover them,D' Argenson and Rouvray are killed while Barbara and Susan and Ian are taken prisoner by them as they doctor is knocked unconscious in the skirmish. The revolutionary soliders set the home ablaze with the terrified doctor still inside.
A young boy Jean Pierre,whom they'd encountered upon arriving in the TARDIS helps the doctor to escape by telling him their friends were taken to the Conciergerie prison in Paris,where Barbara and Susan are awaiting execution at the guillotine as Ian is imprisoned with a cell mate named Webster,who encourages him to send a secret message to an English spy named James Stirling to return to England before Webster dies. After briefly fending off a greedy overseer of a road mending crew barring his lack of papers,the doctor arrives in Paris to a clothier to make a trade: his Edwardian era jacket and his Roman ring for the uniform of regional officer of the provinces. After arranging with the help of the drunken jailer to get Barbara and an ailing Susan out of their filthy,rat infested prison cell with the help of Government Official Lemaitre,who has also managed to cross Ian's name off the execution list after overhearing his conversation with Webster.
While the doctor confers with the megalomaniac Robespierre,Ian and Barbara find themselves taken in by a Jules Renan and his ward Jean-two more counter revolutionaries intent on freeing both Ian and reuniting them all with the doctor. Ian is successful thanks to the doctor in reuniting with all of them. Jules even arranges for a nearby doctor to look after an ailing Susan,and for Ian to confer with a confidant of theirs named Leon. Both the doctor and Leon have been paid off by the shop keep who is using the doctors Roman ring as evidence against him,and even Leon betrays his former companions Jules and Jean to the revolutionaries. Lemaitre shows up with the doctor,revealing that he is in fact James Stirling,after which Ian relays Websters message to arrange a meeting at the neutral Sinking Ship Inn. When their Napoleon Bonaparte himself shows up to discuss a change in government. Knowing they cannot stop an important moment of history the doctor,Ian,Barbara and Susan watch as Napoleon and his men imprison Robespierre and proceed to take over France-before Jules and Jean bid the "mysterious travelers a quite literal adieu on the TARDIS.
Much as with The Invasion with the second doctor, the fourth and fifth parts of this story were animated-this time by a different company. This animation was quite closer to anime-more attuned with natural human movements and done this time in a sepia line tone coloration. The story itself is an involved and rather brilliant historical serial in which each member of the TARDIS crew is forced to take matters into their own hands. In this environment where allegiances are traded with such regularity in fear of the despotic Robespierre, the doctor uses his wiliness in order to put himself into a position of authority through which he can enact just enough social change to free his companions and granddaughter from certain death. Jules Renan comes off as the sympathetic character in this story. While a member of the ruling class, his wish is only for a peaceful revolution as opposed to a violent one-as he cleverly tries to manipulate both sides to satisfy his general preference for peace. James Stirling,himself rather taken with Barbara is left wondering who she and her companions really are as they depart. And since the doctor seems to operate very easily in this difficult historical climate, the mysterious quality of the first doctor is very much on display here as well.