The Doctor reassures K9 that there are (as well as no water and no swamps) no monsters, a nice Kroll reference. K9 states that the radiation levels are within Time Lord tolerances.
The narrator explains that 'of course' the Marshal knows that Merak and Astra aren't traitors really, he's just trying to get them out of the way.
Shapp immediately understands the Marshal's motivation for having K9 recycled: he's annoyed about having been made a fool of when K9 shot out the lighting control box.
The Doctor's own suggestion about the ventriloquist's dummy makes him stop and think:
For all his loudness and flamboyance there was something odd, off-key about the Marshal. Was he a dummy, a puppet of some mysterious force?
Reminds me a bit of his realisation about Uvanov in Robots of Death.
It's been pointed out to me that the Marshal introduces himself as 'The Marshal of Zeos' - such a blatant mistake that I missed it.
There are a dozen ships left in the Atrian fleet, not six. Romana doesn't ask who Columbus is. (Similarly, later on Merak doesn't ask what bees are.)
TD does his best to make the Shadow more impressive, radiating both authority and darkness so that the light seems to dim when he moves. His asteroid resembles 'some fantastic castle in space.'
Astra's smile when the Shadow tells her she'll meet her lover soon is 'like a grimace on the face of a corpse.'
We don't see Mentalis until the Doctor and Romana do. The Doctor works out that there are no Zeons on this part of Zeos, rather than no Zeons at all. They're probably all on the other side of the planet, he says. I realise TD is trying to make the plot a bit more sensible here, but I'm not sure whether this isn't actually sillier than the screen version. It certainly calls irresistibly to mind the image of Lord Percy going 'Perhaps - they're not hiding - at all...'. (The Zeons are mentioned as well as the people of Atrios when the Doctot talks to the shadow later).
The 'banana skin' remark and the discussion about affecting the entire universe are absent, TD perhaps feeling that they anticipate the similar bit when the genuine Key is assembled. Having set up the time loop, the Doctor gets an oak pedestal out of a locker and puts the Key on it. The Marshal's ship is frozen just after launching the missiles - we see them streaking towards Zeos over and over again.
The tunnels in the Shadow's asteroid give it an 'organic' feel, 'like a rotten apple bored through by innumerable worms.' They're carved with gargoyle heads, and it's one of these that the Doctor addresses when he talks to the Shadow. He politely says 'Excuse me' when he walks past himself.
His remark about 'amusement arcade rubbish' is excellently expanded thus:
'All this penny arcade, ghost train rubbish is pretty crude too. Romana can look after herself you know. You won't scare her with spooks.' A giant spider dropped onto the Doctor's shoulder and he flicked it casually away.
(Notice the parallel of the flicking gesture with the way he points over his shoulder on screen when talking about the innocents).
The dungeon he wakes up in 'was a very old-fashioned dungeon; stone-block walls, studded iron door, high barred windows... Clearly the Shadow had traditional tastes in such matters.' It sounds like TD is trying to explain away an ill-chosen set design - but the 'dungeon' on screen is just a cave, it doesn't look anything like that.
The Doctor reflects that Thete (Theta Sigma) isn't really his name, just a 'coding'. Drax is initially a bit offended when the Doctor insists on his title, but the latter placates him by saying 'It's just that I'm used to it.'
Chapter 13, where the Doctor and Drax are miniaturised, is called 'Small World'.
When the Doctor and Drax split up to make their separate ways from the Planet of Evil to Zeos, Drax reminds the Doctor that he built Mentalis and accordingly knows how to turn it off.
When the Planet of Evil has been blown up, and Drax has said goodbye, there's a 'considerable' interval while the Doctor replaces the fake chronodyne 6th segment with the real one. He then places the Key on the pedestal mentioned earlier before having a quick gloat over it and then launching into the megalomaniac bit. It's hinted that he really is falling under the lure of absolute power, rather than just pretending in order to make a point - he 'controls himself with a mighty effort' before saying he's all right.
The reconstituted Astra actually kisses Merak rather than just holding his hand.
