Doctor Who: How The Doctor Got Her Darkness Back

An Impossible Decision

But, even with her speech given, The Doctor seems stumped by her choices, until Shelley makes a plea that no version of The Doctor has ever been able to ignore.

"Please, help me."

And at this moment we see the true danger of this Doctor, a danger posed by every version of the character but never quite approached as plainly as this. The Doctor makes decisions with full knowledge of the consequences, but still acts based on what is before her at the time. Forced to choose between two impossible choices, she fights against the deaths of those people she can see, and hopes whatever consequences come of it can be set right in the future. A hope that she may not always be able to ensure is rewarded.

In this case, those consequences could be the deaths of billions in the future as the Great Cyber-War is set to continue with an 'ascension' of the Cybermen. The Doctor and her 'fam' are in fast pursuit, following Ashad, the Lone Cyberman, in an attempt to stop him bringing the Cybermen back from the brink of destruction. There's no guarantee that she will be able to stop him, and certainly no guarantee that those closest to her will survive the attempt against an enemy that, at best, sees them as spare parts.

This thoughtlessness leads us to believe that, just as Mary Shelley mixed up her creature and its creator in her earlier reference, perhaps the mad scientist who thinks of nothing beyond what she directly affects her now is the true monster of this episode.