Scotland, the near future. Something is smashing oil rigs off the Scottish coast, and UNIT have been called in to investigate. The Doctor discovers a colony of shapeshifting Zygons and their cyborg weapon, the Skarasen, and in the process solves one of Scotland's greatest mysteries...
Elenco: William Hartnell , Patrick Troughton , Jon Pertwee , Tom Baker , Peter Davison , Colin Baker , Sylvester McCoy .