In a Welsh village in 2020, geologist Nasreen Chaudhry (Meera Syal) and her colleague Tony have drilled 20km below the Earth, the furthest anyone has ever reached. However, Tony’s son-in-law Mo feels rumblings and as he goes to investigate he is sucked below the ground.
The TARDIS arrives in a local graveyard where the Doctor notices that the ground feels strange, while Rory finds out from Mo’s wife Ambrose and son Elliot that bodies are disappearing from graves.
Amy and the Doctor investigate the drilling plant, but as the ground shifts, Amy is sucked below. The Doctor tells Nasreen that something else is drilling up and will soon arrive. On his own in the graveyard, Elliot disappears after encountering a strange figure and as Ambrose and Tony look for him they come face-to-face with a scaly monster which stings Tony.
The Doctor and Rory capture a monster and the Time Lord realises she is part of the prehistoric, reptilian Silurian race who once ruled Earth. She reveals that they felt the drilling was a threat and now a war to reclaim the planet is imminent. The Doctor decides to negotiate with the tribe and as Nasreen joins him in the TARDIS it is sucked below ground. With Amy about to undergo experimentation, can she be saved?
Continues next week…