The third script turned out to be The Immunity Syndrome but it had a different title, "The Face Of Eden," to begin with. We had Moonbase Alpha discovering the perfect world...joy all round! But the moment they land on the planet, start to set up home and think that, finally, their long quest is over, they discover that everything starts going wrong. Plants become poisonous, water kills them, and so on...there's something on the planet that is destroying them. In essence it's a very simple thing: it's like a body being invaded by a germ, by a virus. Moonbase Alpha is the virus, the body is the planet, and the planet is simply responding in the way that a human body would to an invasion of this kind, with the added element that the planet is a conscious thinking entity and that it is a desperately lonely entity. All it's ever wanted throughout its ageless existence is the company of another sort of being or some kind of presence that it could communicate with, but the irony is that in the act of communicating with likely prospects that have appeared, it actually kills them, and then having killed them, it expels them. So all of these things are happening and Koenig discovers all of this, and he has this remarkable encounter...which to me is one of the most touching things that I think I've written in the series...where he dons this protective covering, confronts this presence and starts talking to it. It reveals itself to be vulnerable, very human and very destructive, but unknowingly so.
I found this deeply touching and to me it expressed very much the essence of Space: 1999...that villains were not necessarily villains and that disasters were usually the result of cock-ups more than by deliberate intent. This echoes all of the real things in life. Where we did bring in deliberate megalomaniacs and psychopaths, they tended to be less interesting stories. If you just compare any of those episodes like Force Of Life and The Immunity Syndrome with, say, End of Eternity, I think you'll find that they're much better stories.
Comments by Johnny Byrne, abridged from an interview with Tim Mallett and Glenn Pearce and a 1982 interview with Carsten Andresen.