Ask a question in the box below, or search using the box above.

As you enter your question, our massive, TARDIS-sized computers will search out other similar questions. So be sure to check the list that pops up before asking your question. Once you've decided that your question has not been asked before, push the not-so-threatening blue button below.

If you want to ask questions needing speculation or people's opinions, please do it in our Watercooler forum, not here. The main Q&A space is for questions with definitive factual answers. Thanks!

To avoid spoilers in the main Q&A section, please do to not post information about stories that have not been released in the UK, or ask for information about stories that have not yet aired there.

It was a prequel to "The Daleks' Master Plan". At the time, Doctor Who was produced nearly all-year-round. The regular cast would get a week or two off during the season. Usually, it was only one cast member at a time(eg. The Doctor doesn't appear in 2 episodes of "The Keys of Marinus" However, with this episode, the whole regular cast got the week off. And it set up the suspense for DMP. In addition, one Season 2 serial("Planet of Giants") had been edited from 4 episodes down to 3, and they had to "catch up" one episode. It was better to do "Mission to the Unknown", than it was to stretch an existing script out.