Mankind and the Silurians teeter on the brink of all-out war. Can the Doctor ensure the two species’ survival?
Continuing from the previous episode, the Doctor (Matt Smith) and geologist Nasreen Chaudhry (Meera Syal) have taken the TARDIS deep below the ground to the Silurian city where the Doctor’s companion Amy Pond (Karen Gillan), a local man named Mo (Alun Raglan), and Mo’s son Elliot (Samuel Davies) are being held hostage. Meanwhile, above ground, Amy’s fiancé Rory (Arthur Darvill), Mo’s wife Ambrose (Nia Roberts), and Ambrose’s father Tony (Robert Pugh) keep watch over Alaya (Neve McIntosh), a captured Silurian who is the key to freeing the hostages. When Ambrose kills Alaya, the Doctor attempts to prevent Alaya’s sister Restac (McIntosh) from wiping out the human population as revenge by offering to share the planet with the Silurians.
Chibnall was elected by executive producers Steven Moffat and Piers Wenger to write a two-part episode about the return of the Silurians. Chibnall wanted “Cold Blood” in particular to be about the mistakes people make under pressure, and conflict that could come out of protecting a family. The episode is also connected to the series’ story arc, as the crack in the universe returns at the end of the episode.