On to Mission to the Unknown (aka Dalek Cutaway)... This is a rather unusual episode for many reasons: It is the only standalone episode of the original series (other than the feature length anniversary special The Five Doctors) and is the only episode that doesn't feature the Doctor or any of his companions. It was filmed as part of the filming block for the previous serial Galaxy Four and actually came about because the first story in the second season, Planet of Giants, was cut from four to three episodes in post-production. It is also the last story for the show's original producer Verity Lambert.
Due to Planet of Giants being trimmed back by an episode, it was decided to make this standalone episode to fill the gap and to act as a teaser for the massive twelve episode story The Daleks' Master Plan, which would air later during the third season. Terry Nation also hoped that Mission to the Unknown could be used to launch a Dalek spin-off series without the Doctor. While Terry Nation did create a pilot for a spin-off series, it never materialized (pardon the pun). Big Finish Productions has created something very similar with its "Dalek Empire" spin-off audios and has even made Terry Nation's Dalek pilot, "The Destroyers", into an audio drama.
Mission to the Unknown is one of only three serials for which not a single second of off-air footage exists. :( Despite this and the fact that no telesnaps exist for this story, the Loose Cannon reconstruction is amazing. Through creative use of material from The Daleks' Master Plan, set photos, photos of the cast, photos from other serials, and creative compositing of all of the above, Loose Cannon has made it impossible to tell what is actually original material and what they created for this reconstruction.
Add one more to the count of missing episodes for season three to bring the total to 4.
Based on this reconstruction alone, I'm really looking forward to The Daleks' Master Plan, but first we rejoin the Doctor and friends in The Myth Makers... Next time...