The Doctor and Sarah arrive in London to find it deserted. The city has been evacuated as prehistoric monsters appear in the streets. With forces within the army, the government and even within UNIT working against him, the Doctor manages to trace the source of the dinosaurs. But will he and the Brigadier be in time to unmask the villains before Operation Golden Age changes the history of planet Earth and wipes out the whole of human civilization? This novel is based on a Doctor Who story which was originally broadcast from 12 January-16 February 1974. This title features the third Doctor as played by Jon Pertwee with his companion Sarah Jane Smith.