Doctor Who: How The Doctor Got Her Darkness Back

The Cyberium Conundrum

Towards the end of the episode, we learn that the famous poet Percy Shelley had found the Cyberium, a battle computer that the Cybermen used throughout the Great Cyber-Wars of the 26th century. Stolen by agents in the future and sent back in time that humanity might find an advantage, this thing had wormed its way into his psyche and wasn't about to let go. Only a lone, unfinished Cyberman had been sent back to collect it, and it was willing to cut it out of the poet.

"Shelley's going to die if that stuff stays inside him." Graham pointed out, helpfully summing up what we'd just seen.

"Shelley's only one life against all those others." Ryan countered, thinking of the future billions who would die if the Cybermen were to go unstopped.

And you can see in The Doctor's eyes that she both understands Ryan's position and is disgusted by it. She appeals to her companions' sense of right and wrong; she appeals to their selfishness, telling them that his death would change the world so much that they might not even be born. And then, seeing that they aren't equipped to make that choice, The Doctor takes over.

"Sometimes this team structure isn't flat. It's mountainous with me at the summit, in the stratosphere, alone. Left to choose: save the poet, save the universe? Watch people burn now, or tomorrow? Sometimes, even I can't win."