Unable to return to the ship by the caves the group must cross a desert that borders the mountains.  As soon as they start to cross it, they see giant eggs.  They are then attacked by pterodactyls that swoop down at them.  Following what Ki Ki (Brigid Skemp) does, they fall down pretending to be dead.  The pterodactyls soon lose interest.  They next encounter a fight between a T-Rex and a Stegosaurus.  Battling sandstorms, heat and lack of water they continue to make their way across the desert.

When they discover that the planet is rich in diamonds and uranium Brown (George Coulouris) vows to keep Venus from falling into the clutches of strip miners and colonizers.  To do that he believes he must stop everyone from returning to Earth.

As they reach the end of the desert the group finds that the lava from the near-by volcano is setting fires to the jungle.  The fires are putting the rocket ship in danger.

Even though other episodes had some issues with exposed boom microphones and other production goofs this episode was specifically peppered with production mistakes, supposedly 8 of them, although I couldn’t find documented anywhere what the 8 errors were.  It was used as an academic study by the Education Department of Cambridge University into children’s viewing habits and opinions.  Children were then shown the episode and then interviewed to find out if they noticed the mistakes.  A blurb at the end of the episode refers to the study.   

The inclusion of dinosaurs and pterodactyls was achieved by inserting stock footage from the 1955 Czechoslovakian film “Cesta do Praveku”, AKA “Journey to the Beginning of Time”.