Ian Marter

It's ten years since Harry Sullivan left UNIT and gave up his travels in the TARDIS with the Doctor and Sarah Jane. Since then he has been engaged in top secret work, developing antidotes to nerve toxins.

A group of palaeontologists have been savagely attacked while carrying out a study of fossilised dinosaur remains in an underground cave system on twenty-fifth century Earth. A party of troopers and Professor Kyle, the only survivor of the attack, are investigating the deaths of her colleagues...

Reluctantly cancelling his well-earned holiday, the Doctor sets off in the TARDIS to trace and re-assemble the six segments of the Key to Time on which the stability of the entire Universe depends. Assisted by the argumentative Romanadvoratrelundar and K9, he lands on the planet Ribos in...