If ever there was an instance of a reversal in fortunes, this story from Season 15 surely qualifies. I couldn’t enjoy the VHS release at all as a teenager (though it is perhaps fairer to say that I wasn’t willing to give it a chance), and when the BBC in their wisdom decided to release the adventure on DVD alongside the sole episode of 1980s spin-off K9 and Company I spent as long as I could deferring buying the story.
That turned out to be a mistake. Not only was K9 and Company surprisingly enjoyable (while obviously nowhere near as good as Doctor Who!) but The Invisible Enemy itself is a gem of a story. The story explores an inter-spatial virus that travels through energy exchange (basically, lightning) who has planted the host virus inside the Doctor, and infected a number of human researchers on a outpost in the solar system, intending in due course to take advantage of human colonists spreading throughout space to in turn spread itself through the universe.
The story introduced a number of novelties, of which the greatest is K9, the dog-shaped computer belonging to the character of Professor Marius (“He knows everything I do!” “Yes master … and more.”) – so popular would the character be with the viewing audience, that the final scene was rewritten so that the robotic canine could join the TARDIS crew. He certainly gets off to a lightning start, and is justifiably the brightest spark in a very good story. While it is perhaps true that the producers came to rely on him too much in future, I rather enjoyed K9 being part of the TARDIS crew.
The show also features some excellent touches – Leela’s natural immunity to the virus gives her a chance to shine; while the Doctor’s ingenious suggestion to create temporary minaturised clones of himself and Leela to investigate his own neural pathways (dodgy science aside) make for unusual but excellent television. Yes … there is the elephant in the room of the akwardly imagined virus (accidentally increased to human size by the end of episode 3) – but the story is nevertheless a superb and creative imagining, not least as the Doctor changes his approach between a virus that has the right to live, and the monster that plans cosmic destruction.
While you undoubtedly need to suspend your disbelief, The Invisible Enemy is a fine example of this period of Doctor Who, and worth watching just for the scenes featuring K9. I was glad to have the chance to reappraise it!