There's very little plot in this episode, which really only exists to finish the job of replacing all the bits of exploded Liberator. The genius scientist Doctor Plaxton has designed an amazing new engine, which will allow the Scorpio to go faster than anybody else - if they can get hold of it. Unfortunately for the gang (and for the viewer, arguably), the only people who will fund Doctor Plaxton's research are the Space Rats, a gang of brain dead speed freaks, who couldn't carry a plot if they tried. They look a bit like refugees from one of the latter two Mad Max movies, or perhaps grown up cast members of The Tribe - just without any of the things that made either of those franchises any fun. It's not a bad episode as such, just lacking in subtlety; and it's all too obvious that it really is nothing but another stepping stone to "replacing" the Liberator. If you're making a TV show, I think the lesson to take away from this is to make damned sure the final curtain really is falling before you blow up all your stuff. It does rather test the audience's patience if they have to wait for you to get it all back again the following year.
( ... )
( ... )