While the Doctor and Liz try to find a cure to the virus spread by Baker, the Young Silurian kills the Old Silurian and takes control of his people.
Quest roles:
Nicholas Courtney(Brig. Lethbridge-Stewart), Pat Gorman(Soldier), Peter Halliday(Pletrac), Paul Darrow(Tekker), Geoffrey Palmer(Administrator), Richard Steele(Sergeant Hart), Alan Mason(Corporal Nutting), Brendan Barry(Hospital Doctor), Peter Miles(Nyder), Nigel John(Young Silurian), Simon Cain(Silurian), Derek Pollitt(Private Wright)