Target: The Invisible Enemy

Not one of my favourites, this. The narrator spends too much time dumping facts about Titan and Saturn on us in the early pages, although TD does give us a plausible picture of Lowe as a fussy, precise man (exactly what Sheard's portrayal leads us to assume).

Leela can get the TARDIS to the Bi-Al Foundation because the Doctor has instructed her in basic takeoff and landing procedures, just in case.

The Foundation appears to be a business proposition, funded by various 'conglomerates'. Odd then that nobody seems to be charged any fees. We're also told more about the 'spaceniks', who make a nuisance of themselves stowing away to see the planets, and then have to be sent home at great expense. They're 'the descendants of the hippies and beatniks of the late twentieth century' - the spiritual descendants I presume, unless he's telling us that Cliff and Jo Jones are the root cause of the problem.

There's extra emphasis on the idea that the Kilbracken technique is one of holographic cloning, and that this is why it can reproduce clothing as well as bodies.

The lines in the 'bit of a mongrel' conversation are distributed slightly differently between Marius and PVC Nurse.

The cavern in which the Nucleus is lurking extends as far as the eye can see, and has silver pillars holding up the roof.

The narrator raises a question in our minds about the cause of the Doctor's immunity to further infection once the Nucleus leaves his brain - it might be because he's survived such a massive attack, 'or perhaps for some other reason'. Thus we are properly primed for the Doctor's explanation about the Leela clone dissolving in his bloodstream, making it seem more convincing.

On Titan, Safran is full of pride at having prepared such a good breeding environment for the Purpose. At least he dies happy, then. K9 deals with the guard that he decoys away by losing him in the maze of corridors (some task given the amount of noise K9 makes in his early stories).

The hatching virus creatures are described as like 'malevolent dragonflies' - possibly my first encounter with the word malevolent. The Nucleus has grown to massive size, and wallows frighteningly across the tank towards the door to get at the Doctor.

The TARDIS does not partially dematerialise, then return for Leela and K9 - they manage to dash inside just after the Doctor.

In sum, an unobjectionable adaptation, but not one of the classics.