The the Professor and his compatriots have installed their experiments below the ground in a sealed bunker powered by its own nuclear reactor. Sadly she comes to learn that Grover is part of the conspiracy with the Professor. After being put in an interrogation chamber, she wakes up to find herself on a spaceship populated by Utopian intellectuals believing they are journeying with chosen humans to repopulate a newly discovered Earth-like planet in an attempt not to make the mistakes of Earth's conflicted society. While imprisoned here for her assertion this concept is ill founded,Sarah finds out the airlock is actually doorway outside and they aren't on a spaceship at all. While investigating with the Brigadier at Trafalgar Square Station he discovers Whitaker's base and,eventually the entirety of the plan: Whitaker is heading up Operation Golden Age,using a time field to reverse time on Earth to a more primitive state where a select few humans can build a more egalitarian environment. And that Grover,Finch and even UNITS own Captain Yates are all coordinators of this affair. In the end Whitaker and Grover are sent back to their "golden age" by their own device as it is disconnected from the reactor by the doctor. Finch is court-martialled,Yates put on temporary sick leave and the doctor tempts Sarah Jane Smith to accompany him on another journey in the TARDIS.
Intended obviously as a showcase for the presence of dinosaurs, the result is the one story of the classic Doctor Who era where the special effects completely fall apart-in particular overuse of an extremely poorly realized Tyrannosaurs. Even so the dinosaurs themselves are only a mild catalyst for the true action of this story. Aside from the critical FX gaffe, this is one of the most consistently strong and enjoyable stories of the third doctor era. The story of eugenics desperate enough to prevent the birth of billions of human beings due to ecological and sociopolitical strife is very much the flip side of the story presented in The Green Death,where humanist environmentalists are depicted as heroic-where higher profile ones are portrayed as villainous egoists here. While the plight and betrayal of the misguided Yates was heartbreaking for Whovians I'm sure,this presents enormous growth for the Brigadier. In this story he is presented as the doctors loyal and capable companion-in an atypically and fully agreeable manner willing to listen to all sides before making his moves,military or otherwise. Shows the characters growth from very doubting to an expansion of mindset. Again Sarah Jane Smith is given almost more to do then they doctor. She doesn't need him to rescue her. In fact she actually helps him save all of human kind from a fate worse than death: never having even existed.