The Doctor and Sarah Jane (Elizabeth Sladen) arrive in a deserted London besieged by dinosaurs. The Doctor suspects someone is tampering with Time and, with UNIT’s help, comes up with a plan. They are introduced to Sir Charles Glover (Noel Johnson) and General Finch (John Bennett). In a secret lab, Prof. Whitaker (Peter Miles) is opening a Timescoop and importing dinosaurs to evacuate the city. He is being aided by a disillusioned Captain Yates of UNIT (Richard Franklin), who is still suffering from PTSD because of the mind-control he experienced in the story The Green Death.
Sarah investigates but is captured by Sir Charles, who is working with Professor Whitaker. She awakes on a vast spaceship. The crew explains that she is en-route to an Earth-like planet—new and clean—with a collection of colonists. Sarah doesn’t believe it, and when she tries to say so, they condemn her to re-education. This Operation Golden Age is a huge conspiracy. They have emptied London so the chosen people in the fake spacecraft will be the only ones within range of the Timescoop when it is activated for the final time, sending them all back to a perfect age before pollution, moral decay, etc. etc.
Sarah escapes from the bunker. She is apprehended, but her escape alerts some of the passengers. Yates, breaking with the conspiracy, reveals the truth to the Doctor and the Brigadier. Yates is overpowered, but General Finch is incapacitated. The Doctor and the Brigadier confront the conspirators as the victims arrive and demand an explanation. Though the Timescoop is activated, the Doctor as a Time-Lord has the power to sabotage it. Only Whitaker and Grover are sent into the past.
Many recognizable London locations were used, and the empty streets in the first episode, available in black and white, seemed like something from the Fifties. But the dinosaurs romping about were not impressive, Sharp-eyed fans complained that the T-Rex was really an Allosaurus and they had been short-changed. The plot itself seemed far-fetched, even to Doctor Who fans. But if the dinosaurs had even come close to those of Willis O’Brien or Ray Harryhausen, nobody would have noticed. There was a nice line-up of fan-favourites—a Pterodactyl, a Stegosaurus, a Triceratops, an Apatosaurus they had the decency not to call a Brontosaurus, and the Allosaurus with delusions of T-Rex—but they suffered from wobbly sets, disappearing body parts, visible puppet strings, and feet that did not seem to be bearing weight on the ground. Why do you think the T-Rex in Jurassic Park placed its huge foot in the squishy mud in a full-screen close-up? This was to tell you that Spielberg’s dinosaurs walk the earth.