Episode 5
Series Episode Number: 276World Premiere: Sat 6 Jun 1970 - 5:15pm BST [BBC One] (United Kingdom)
First Broadcast: Tue 4 Nov 1975 - 6:30pm CST [WTTW 11 Chicago]
Running Time: 23 minutes 42 seconds
5.40 Million (UK)
Chart Position: 54 () (UK)
Recorded on Thu 21 May 1970 in TC3 / TC6
Archive State: RSC conver
In the parallel world, Earth's crust has been penetrated, releasing terrible forces from within the Earth. The Doctor must escape back to his world to prevent the same catastrophe.