Overview
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.
| Actor | Age then | Age now | |
|---|---|---|---|
 | 50 | May 20, 1996 (76) | |
 | 29 | June 5, 2012 (71) | |
 | Nicholas Courtney Brigadier Lethbridge-Stewart / Brigade Leader Lethbridge-Stewart Birthday: December 16, 1929 | 40 | February 22, 2011 (81) |
 | 28 | 83 | |
 | 56 | July 14, 2015 (101) | |
 | 35 | January 10, 2025 (90) | |
 | 30 | March 3, 2004 (63) | |
 | 36 | August 11, 1998 (65) | |
 | 26 | 82 | |
 | 32 | September 22, 2015 (77) |