The obvious baddys who Sarah met in the last episode come in and tell Robot to kill Sarah, but it says this conflicts with its Prime Directive. I don't understand how killing Sarah would break the Prime Directive, but it means that Sarah doesn't get killed by Robot.
Sarah tells the Doctor about Robot so Harry goes to spy on the obvious baddys until the Brigadier has enough evidence to go and arrest everybody.
The Doctor goes to visit Mad Scientist Professor Kettlewell, who says that if they force Robot to go against the Prime Directive then he will go mad. I mean that Robot will go mad, not Professor Kettlewell - he's already mad. Or at least his hair is.
We then see Robot breaking the Prime Directive by
interfering in the internal development of another civilisation killing a manny and stealing his paper. The juxtaposition between this scene and the one immediately preceding it represents a clever use of dramatic irony by the writer.
Robot then goes to visit Professor Kettlewell and tells the Professor about his problems - he is a sad robot.
Sarah visits a silly manny who thinks mannys shouldn't wear trousers and who wants all mannys to do what he wants. At least I think that's what happens in that scene, I got a bit confused. But I got the point of the scene which is is that he's another obvious baddy.
The Doctor and the Brigadier visit the obvious baddys and they tell the Doctor that Robot is dead.
The Doctor doesn't believe them but he can't find where they've hidden Robot. Harry visits the obvious baddys too, but he's in disguise...
Harry is disguised as Steed from The Avengers. I'm not sure if the obvious baddys are fooled or not.
The Doctor goes back to Professor Kettlewell's house and meets Robot there. But then Robot tries to kill him so there is a cliffhanger!