The Invisible Enemy

At a key point in 'The Invisible Enemy' the Doctor discovers that cloning experiments first took place in the year 3922 (or some similarly far-flung date), a gentle reminder that recent advances in genetic science have come at us far quicker than could ever have been expected. That isn't to imply that 'The Invisible Enemy' explores cloning in any serious way: it doesn't. But it does demonstrate the wonderfully throw-away approach to science in Doctor Who stories, or what in Star Trek is called 'techno-babble'. But where Star Trek is quite earnest and serious in its approach to 'science', taking it all 'very seriously', Doctor Who stories often seem to fling 'real' science facts into the mix in the way you might fling chocolate chips into a dough mixture: you don't need to be precise, because all that really matters is that you don't forget to put them in. 

The reason 'The Invisible Enemy' is still entertaining is the combination of witty dialogue and eye-catching design. Tom Baker frequently proves to be the saving grace of Fourth Doctor stories, and here is no exception. Both the Doctor and Leela are served well by a script which is clever, slightly ironic, and full of good dialogue ("You megalomaniacs are all the same"), and save for a few dud lines (usually where the script is desperately trying to cover some distance in a short space of time with exposition from either Leela of the Swarm) Bob Baker and Dave Martin turned out a solid (if not classic) story.

However what stands out in 'The Invisible Enemy' is the time that appears to have gone into giving the story a distinctive look and atmosphere. A high-angle shot of the three infected astronauts in their space-suits, for example, succeeds in stretching the capabilities of a shot-on-video studio-based TV story into the realms of the filmic. 'The Invisible Enemy' isn't cinematic by any stretch of the imagination, but there are certain shots early on that leave a big impression. The cliff-hanger to episode one, the special effects shots at the very beginning of the story, and the model-shots of the eggs before they hatch, are all particularly effective. And other, smaller details shouldn't be ignored: the decals used in the moon base ('Oxygen' and 'Level 4X', etc.) have a pleasing future-retro feel, and Professor Marius' spectacles are wonderful.

There is a lot to like in 'The Invisible Enemy', and even though certain elements would make even the most hardy of viewers wince (the inside of the Doctor's brain, and the virus in it, for example, are far too tacky) overall it is a successful and enjoyable Doctor Who adventure.