The original notes talk about the return of the Daleks, and possible ways it could be handled:

"Perhaps this story can feature the return of an old foe, maybe the Daleks -

leads to two possibilities -
a) They appear at the end on an episode , probably 1 or 2 at the latest, and this is a standalone story, or
b) They appear, are "revealed" if you will, at the end of the story, so as the story ends on a cliffhanger that is resolved in the following story. (note - possible too similar to the Frontier in Space/Planet of the Daleks bridge, as well as being bloody hard work.)"

The story is also notable by the absence of Jo Grant, which was because this story was set after she had left, as the notes went on to say:

"Features the third Doctor on his own (set between The Green Death and The Time Warrior) to make the story a bit more flexible - no need to feature a companion to any extent, although there could be some UNIT involvement."

This is also why the season 11 (through to 17) logo and titles were used for each episode, rather than the original Pertwee version that had been used before.

Next, although the story is almost word for word the same as in the original outline, there were some interesting lines that were not used in the end.

Brigadier: I smell a rat
Doctor: I smell a much bigger cat; a cat who's pulling the strings.

Dalek: Doctor, now you are ours!!
Doctor: [A victim of] my own irrepressible curiosity and thirst for knowledge.

Finally, this story is set whilst the Daleks are fighting the Movellans, ( perhaps even during the Doctor's fourth incarnation's trip to Skaro in Destiny of the Daleks). The purpose of the experiments to create a gas that can sweep clean the mind of a human, making him a mindless slave to the Daleks in their "War Effort"…