In the year 2020, in the small Welsh town of Cwmtaff, a driller named Mo (Alun Raglan) is pulled underground when the ground opens beneath him at a mining operation, where a drill is descending deeper in the Earth than ever before. The Doctor (Matt Smith), Amy (Karen Gillan), and Rory (Arthur Darvill) land the TARDIS there instead of Rio de Janeiro where they wanted to go. The leader of the mining operation, Doctor Nasreen Chaudhry (Meera Syal) is studying minerals beneath the Earth that are 20 million years old. She is assisted by Tony Mack (Robert Pugh). When an earth tremor opens the ground, Tony and Amy fall into it. Tony is rescued, but Amy is pulled down. When the Doctor learns that three life-forms are coming up the drilling shaft, he barricades everyone in the church. He assures Rory that he will get Amy back.

Up come three humanoid reptilians called Silurians. The Doctor has met creatures like this before. One seizes young Elliot (Samuel Davies) and takes him down, but the Doctor and Rory subdue another and now both sides have a hostage. The captured Silurian, Alaya (Neve McIntosh) says she was awakened from ancient sleep by the drill. The Silurians, as they predate humans by millions of years, believe the Earth belongs to them, and the drilling was an attack upon them. The Doctor decides to take the TARDIS down the hole and Doctor Nasreen goes with him. Amy awakens on a dissecting table. The Doctor and Nasreen arrive to find an immense Silurian civilisation deep in the Earth. To be continued.

The Silurians appeared in Doctor Who and the Silurians, with John Pertwee in 1970 and in Warriors of the Deep, with Peter Davison in 1984. Meera Syal, who plays Nasreen, had been a Doctor Who fan since childhood. As opposed to some earlier forms, these Silurians were beautiful and did not hide the actors’ faces. The original Silurians had a third eye, but so did Davros, and that idea was scrapped. Amy’s fear and claustrophobia were real on the part of Karen Gillan as she was dragged down into a pit of sand. The episode received mixed reviews. Some like the new Silurians, some missed the old, but everyone liked their cool reptilian whiplike poison tongues.