UNIT is providing security cover at an experimental drilling project at Eastchester, designed to penetrate the Earth's crust and release a previously untapped source of energy. Soon, however, the drill head starts to leak an oily green liquid that transforms those who touch it into vicious primeval creatures with a craving for heat. The Doctor is accidentally transported "sideways in time" by the partially repaired TARDIS control console into a parallel universe where the drilling project is at a more advanced stage. Thwarted by his friends' ruthless alter egos, he works to save both universes.
Douglas Camfield
Barry Letts
Don Houghton
Jon Pertwee
The Doctor
Caroline John
Liz Shaw / Section Leader Elizabeth Shaw
Nicholas Courtney
Brigadier Lethbridge-Stewart / Brigade Leader Lethbridge-Stewart
John Levene
Sergeant Benton / Platoon Under Leader Benton
Olaf Pooley
Professor Stahlman / Director Stahlman
Christopher Benjamin
Sir Keith Gold
Sheila Dunn
Petra Williams / Dr Petra Williams
Derek Newark
Greg Sutton
David Simeon
Private Latimer
Derek Ware
Private Wyatt
Walter Randall
Harry Slocum
Ian Fairbairn
Bromley
... and 13 more
CinemaSerf
I found this to be very similar to the previous "Ambassadors of Death" series with the "Doctor" (Jon Pertwee) and his assistant "Liz" (Caroline John) recruited by the "Brigadier" (Nicholas Courtney) to help solve some mysterious goings-on at another top secret government establishment. This time, it...
BBC