Synopsis
The Doctor and Sarah Jane Smith arrive in a deserted London plagued by looters and lawlessness, where UNIT is assisting in maintaining martial law. The regular army, headed by General Finch, has evacuated the entire city and issued a command that all looters will be shot. The Doctor and Sarah are arrested on suspicion of looting, but are rescued by Brigadier Lethbridge-Stewart who is heading the UNIT operation, and the Doctor begins to combat the monsters, which have necessitated the evacuation. Dinosaurs are appearing all over the city, causing havoc, but no one can account for their sudden appearances and disappearances.
The Government has relocated to Harrogate, and the Army has undertaken an orderly evacuation of London's population and is trying to maintain law and order in the evacuated zone. The dinosaurs, of various types – Pterodactyl, Stegosaurus, and Tyrannosaurus Rex – are being used as terror weapons to compel the authorities to evacuate the city. The Doctor encounters a Stegosaurus moments before it disappears. He also encounters a medieval peasant from the reign of King Richard the Lionheart. Each disappears in a time eddy, and he begins to suspect that someone is tampering with time, deliberately bringing the dinosaurs to London with the intent of causing the chaos.
In a hidden laboratory, a scientist named Professor Whitaker is operating the secret Timescoop technology. He is being aided by Captain Mike Yates from UNIT, who is recovering from a nervous breakdown caused by events depicted in The Green Death. Mike feels the Doctor would help with Operation Golden Age, but Whitaker is unconvinced and orders Yates to sabotage the device the Doctor is building to capture a dinosaur. This imperils the Doctor, when he unexpectedly encounters a Tyrannosaurus Rex, but the creature is nevertheless captured. However, General Finch - also part of the conspiracy - secretly frees it.
Sarah Jane meets with Sir Charles Grover, an ecologist MP who is the Minister with Special Responsibilities, the only member of the Government to have remained in London. She is kidnapped by him, and when she awakes is astounded to find herself on a vast spaceship en route for another planet. The passengers and crew are all minor celebrities who support the ecology movement and want to start new lives based on the movement's political agenda. They are en route for New Earth, a planet where mankind can begin again, closer to nature. The spacecraft is one of a fleet carrying hundreds of people to this new world, and they condemn Sarah to be re-educated into thinking the way they do.
The Doctor searches London for the energy emissions of the Timescoop, in his new vehicle, the Whomobile. Beneath Trafalgar Square tube station he discovers the base used by Whitaker, but is forced away when a pterodactyl is set on him. When he returns, with the Brigadier, all signs of occupation have been hidden. Operation Golden Age is revealed to be a broad conspiracy including Whitaker, Yates, Grover and Finch as its co-ordinators. They have emptied London, so that the chosen people on the "spacecraft" (actually, a dummy ship concealed in a bunker under Central London) will be the only people within the area Timescooped back into the past, to begin the human race anew, without pollution and over-population. Whitaker has discovered how to reverse time, so that none of humanity, save for the chosen elite, will ever have existed.
Finch tries to discredit the Doctor, who will not support the plan; but the Doctor realises that Yates is the traitor within UNIT. Sergeant Benton lets the Doctor escape, and when he is recaptured the Brigadier asserts his authority to take the Doctor into UNIT custody rather than the regular Army’s. Meanwhile, Sarah escapes from the fake spaceship, but is apprehended by Finch. Even so, her escape alerts the passengers to the deception.
Finch and Yates reveal their plans to the Doctor, Benton and the Brigadier. The Doctor and the Brigadier thereupon confront Grover and Whitaker, and, simultaneously, the duped environmentalists from the fake spacecraft arrive and demand an explanation. In the ensuing fight, Whitaker and Grover are the only ones transported back through time to the Golden Age, which they had sought to create.
Back at UNIT HQ, the crisis is over but there are still problems to deal with. Finch will be court-martialled, but Mike Yates is to be given extended sick leave and offered the chance to resign quietly. The Doctor reflects that Grover's motivations in wanting to fight pollution and environmental degradation were honourable, but that he took the scheme too far in endangering all of mankind and all of its civilisations. He decides it is time for a holiday, and offers to take Sarah Jane to the holiday planet, Florana.
Read more about this topic: Invasion Of The Dinosaurs