Doctor Who and the Cave-Monsters (Doctor Who)

While caving in Derbyshire, two pot-holers are attacked by a huge creature and one is killed. At the nearby Wenley Moor nuclear research centre, which is built into the same caves, there are strange power losses threatening the reactor. Not only is everyone at a loss to explain these incidents but there is also a high number of breakdowns involving staff members.Now exiled to Earth and working for UNIT, the Doctor and his assistant Liz are sent for. As the surviving pot-holer begins to make cave-paintings in his ward the Doctor discovers not only a Tyrannosaurus Rex but a colony of Silurians - intelligent, walking lizards who have been dormant for millions of years. Now they have awoken to find that mankind has replaced them as the rulers of Earth - and they want it back.Can the Doctor find a way of thwarting their plans or will humanity be wiped out to usher in a new Age of the Lizards?