Doctor Who: The Newbies Guide
Mission to the Unknown
This is the second story of Season Three. It is a single episode that does not feature the Doctor or his companions. The episode does not exist in the archives.
Where does this fit?
This story does not feature the Doctor, but happens some time before The Daleks' Masterplan later in the season.
Recurring and Historical Characters
The Daleks are a race of mutants encased in powerful cyborg bodies whose shape is reminiscent of pepperpots. The Doctor first encountered them on their home planet of Skaro in The Daleks (Classic Series Season 1). In that story, they were confined to a single city on Skaro and the Doctor thought he had defeated them forever. He later encountered them in The Dalek Invasion of Earth (Classic Series Season 2), where they had conquered the planet Earth, and The Chase (Classic Series Season 3), when they had acquired a time travel machine and were chasing the TARDIS through time and space. In both instances, he managed to defeat them.
None, unless you want to revisit the Daleks' past appearances.