office, the Doctor finds a globe that depicts the Earth's continents as they were 200 million years ago along with notes about the Silurian period of Earth's history. Quinn is discovered dead. The Doctor retrieves the signal device from his body and is surprised by the wounded Silurian creature. The Doctor tries to talk to the creature, but it runs away. Baker is captured and interrogated by the Silurians about the strength of humans. The Doctor and Liz follow Baker's route and open the entrance to the Silurian base with the signal device, where they find him in a locked cage. They witness a Silurian being revived from hibernation by a machine, explaining the energy drains that the reactor has been experiencing. Masters, the Permanent Under-Secretary in charge of the centre, arrives. The Doctor tells them about the Silurians in the caves, urging peaceful contact. However, this is ignored when Quinn's assistant reveals that he was killed by the Silurian he held captive. The Doctor attempts to warn the Silurians, but they put him in a cage. The older Silurian tells the Doctor how their race retreated underground when they saw the Moon approaching Earth millions of years ago. The hibernation mechanism malfunctioned, and they did not revive until a new power source was discovered. A young Silurian orders Baker infected with bacteria before he is released. The older Silurian releases the Doctor, giving him a canister of the bacteria so he can discover a cure. The younger Silurian usurps and kills the older one for this act, becoming the new leader. The Doctor reaches the centre and warns everyone to stay away from Baker, who collapses with the infection. Masters decides to return to London, unaware that he has been infected. Baker is taken to a local hospital and dies. The Doctor begins to work on a cure. Masters has reached London and eludes the search parties looking for him. The bacteria spreads, and deaths begin. The Doctor finds a cure, but the Silurians attack the centre and abduct him. Liz discovers the formula for the cure, which is soon mass-produced and distributed. The Silurians intend to force the Doctor to use the reactor to provide power to a weapon to destroy the Van Allen Belt and make the Earth's environment hostile to humankind. The Doctor overloads the reactor and tells the younger Silurian that the area will be