When Terry Nation wrote The Dalek's Masterplan, he was under the impression that Vicki was still part of the main cast. If she were, she would have been killed off in this episode and not Katarina.
Sara was originally conceived as Brett's lover, but this was later amended to make them siblings.
This episode was wiped by the BBC and no copy of it is known to exist.
This episode takes place on Kembel and in Central City on Earth in 4000.
Daxtar was originally named Tom, then Dexter. In the original script, he elected not to betray the Doctor's party and was murdered by the Daleks for helping them to escape to Mira.