Neil Gaiman, the writer of this episode Neil Gaiman spoke about how his episode was conceived with a mission to make the Cybermen scary again.
Speaking to Reviewer.fr he said: “Steven asked me to write a new episode and I said no because I was too busy. And then he wrote and asked if I wanted to make the Cybermen scary again. And I thought back to when I was six or seven years old: ‘The Moonbase’, ‘Tomb of the Cybermen’ … when I saw them when they were first broadcast. The Cybermen were far more frightening than Daleks, because they do not make noise. Daleks move in all directions, shouting ‘Exterminate’, etc.. With Cybermen it’s different. You turned around and bam! There were Cybermen. It’s scary.
“I told [Moffat] that I would revive the Cybermen for the 50th anniversary year and everything that has happened since, and see what I could do. I do not know if it will work, we’ll see. This will be a stand-alone episode, it will be the penultimate episode of Series 7. It has a beginning, a middle and an end.”
Gaiman also stated that the title of the episode, which is currently believed to be The Last Cyberman, could still change: “‘The Doctor’s Wife’ was’ Bigger on the Inside’, up to two weeks before release. It could be anything,” he said.
Set reporters have also revealed some plot details for the episode. (WARNING: SPOILERS AHEAD)
Gabundy describes the setting of a scene:
The scene seems to be set in a (maybe abandoned?) theme park called Hedgewick’s World. The park map showed rollercoasters, ghost trains and boating lakes and sand dune rides. This particular scene was inside Natty Longshoe’s Castle – a faux medieval fortress complete with dressed dummies, instruments of torture and signs pointing to shops and exits (they were props, not Castell Coch items). It seems a rag-tag bunch of fighters are taking refuge here from a Cyberman attack. Jenna was wearing a military insignia on her jacket, sort of like a set of gold wings with branches circling.
Timeboy provides some more details:
The Cybermen appear out of smoke towards Clara, creeping slowly towards her. She grabs a mace, and swings it all over the place, hitting them. It doesn’t do anything, so she accepts defeat and throws the mace away in anger, then dodges the Cybermen and escapes! Army people with big guns come and shoot the Cybermen, and the Cybermen fire their arm guns back, hitting some of the soldiers.