The Doctor and UNIT investigate a deadly infection lurking underneath the Welsh mining town of Llanfairfach. It's an adventure that will change Jo Grant's life forever...
The Doctor
Jo Grant
Brigadier Lethbridge-Stewart
Sergeant Benton
Captain Mike Yates
Cliff Jones
Stevens
Elgin
Hinks
Dai Evans
Dave
Bert
Nancy
Milkman
Hughes
Fell
BOSS (voice)
Minister of Ecology
Cleaner
Yates' Guard
Guard
James
