10 Dropped Doctor Who Plot Threads We'll Never Get Answers To

Series 5's Chris Chibnall-penned two-parter The Hungry Earth and Cold Blood brought the Silurians back to Doctor Who, in a story revolving around an enormous Silurian civilization living beneath the surface of the Earth.

However, they're not entirely satisfied with their current housing conditions. The Silurians want to move above ground and live on the actual surface of the planet, rather than underneath it. As such, Cold Blood includes a plotline about the humans and the Silurians trying to work out an agreement that will allow the two species to share the Earth. But in the end, this situation proves too difficult to resolve.

And so, the Doctor proposes a solution: the Silurians will go into hibernation for 1,000 years, and afterwards, they will emerge, and the human race must be ready to share the planet with them. This is where the story ends, but in the ten years since Series 5 aired, we haven't yet revisited exactly what happened when the Silurians woke up.

And this has left many questions dangling. Were the humans ready to accept the Silurians? Were they not ready? Was there a war? There's a bit of narration at the start of Cold Blood that hints at a peaceful co-existence, but the finer, far more interesting details of this storyline are still frustratingly unclear.

Chibnall even revisited the Silurians in Series 7's Dinosaurs on a Spaceship, but he chose not to reference the events of Cold Blood. In all likelihood, that piece of narration is all we're going to hear on the matter.