‘Hand Of Fear’ is probably most notable for marking the (first) departure of Sarah Jane Smith after two Doctors and an awful lot of screaming, although it’s also a pretty peppy story which traverses 150 million years and two galaxies.
The TARDIS materialises in a quarry on Earth (one of the few times in the series a quarry on Earth is just that) just in time for Sarah Jane to be buried in an explosion. When they dig her out, she is clutching a fossilised hand. The hand belongs to Eldrad, an alien super villain from the distant past. Apparently dead, the hand exerts a malign influence over Miss Smith, later using a massive dose of nuclear power to reconstitute itself into a rather foxy silicon based life form, a curvy, haughty charcoal briquette.
Forcing the Doctor to take her back to her own planet, Eldrad is killed by a trap set for her by the long dead people of her now empty world of origin. Undaunted, she reconstitutes herself into a much bumpier, even more bonkers male who, realising there is nothing left for him on his own planet, decides to return to Earth and conquer us instead, the cheeky bastard. The Doctor’s not having this, of course, so he trips him up with his scarf and sends him plummeting into a bottomless pit. End of.